EDIT Thanks to Cornel for this great link, it shows a page with various flavours of the updates for Revit 2015:
http://revit.downloads.autodesk.com/download/2015RVT_RTM/UR6/AutodeskRevit2015UR6andA360CollaborationforRevitv3downloadlinks.htm

Here is the link for Revit 2015 R2:
http://download.autodesk.com/SWDLDDLM/Updates/Revit/UR6/Autodesk_Revit_2015_Update6_forR2.sfx.exe

Readme:
http://download.autodesk.com/SWDLDDLM/Updates/Revit/UR6/Autodesk_Revit_2015_R2%20_UR6_Readme.htm

Enhancements:
http://revit.downloads.autodesk.com/download/2015RVT_RTM/UR6/Enhancements_List_RVT_2015_UR6_forR2.pdf

Autodesk® Revit® Architecture 2015 Updates
 – Corrects the behavior that caused view templates to apply incorrectly for some views, if a temporary view
template was also applied to the view.*
– Improves stability when editing a families.*
– Improves loading and editing families which contain extensible storage.*
– Allows type parameters in upgraded families to swap from one type to another.*
– Improves stability when upgrading a project which contains corrupt families.*
– Improves notification reliability when closing a workset in which a rvt file link has been placed.*
– Improves stability while opening the Material Dialog.

Autodesk® Revit® MEP 2015 Updates
 – Improves highlighting of circuits in the plan view from a panel schedule or System Browser.*

Autodesk® Revit® API 2015 Updates
– Improves querying of point cloud on RCS files using the Revit pointcloud API.*
Direct links copied here: 

Please refer to the Readme links for installation and update enchancement information.

Revit 2015 R2
Link Description
Link
File Name
Readme
Autodesk Revit 2015 Release 2 UR6 Readme.htm
UR6 for Existing Installs
Autodesk_Revit_2015_Update6_forR2.sfx.exe
UR6 for inclusion within Deployment Image
Autodesk_Revit_2015-x64_Update6_forR2_Deployments.exe

Revit Architecture 2015 R2
Link Description
Link
File Name
Readme
Autodesk Revit Architecture 2015 Release 2 UR6 Readme.htm
UR6 for Existing Installs
Autodesk_Revit_Architecture_2015_Update6_forR2.sfx.exe
UR6 for inclusion within Deployment Image
Autodesk_Revit_Architecture_2015-x64_Update6_forR2_Deployments.exe

Revit MEP 2015 R2
Link Description
Link
File Name
Readme
Autodesk Revit MEP 2015 Release 2 UR6 Readme.htm
UR6 for Existing Installs
Autodesk_Revit_MEP_2015_Update6_forR2.sfx.exe
UR6 for inclusion within Deployment Image
Autodesk_Revit_MEP_2015-x64_Update6_forR2_Deployments.exe

Revit Structure 2015 R2
Link Description
Link
File Name
Readme
Autodesk Revit Structure 2015 Release 2 UR6 Readme.htm
UR6 for Existing Installs
Autodesk_Revit_Structure_2015_Update6_forR2.sfx.exe
UR6 for inclusion within Deployment Image
Autodesk_Revit_Structure_2015-x64_Update6_forR2_Deployments.exe

BIM360 Revit 2015 Add-in link:
http://download.autodesk.com/SWDLDDLM/Updates/BIM360Addin/2015/4.35.1209/B3AddinRvt.msi   

Recap 1.4.2.2_to_1.4.2.8 link:
http://download.autodesk.com/SWDLDDLM/Updates/ReCap/1.4.2.8/AutodeskReCap_1.4.2.2_to_1.4.2.8_SP_x64.msp

If you forget to close Revit before trying to install the Glue update, you might get this error. Just close Revit, remove the BIM360 addin and then reinstall it.

    

Here is the persistent crash – it was happening when any RVT file was closed:
View Revit 2015 Update 5 crashes when closing any file 

Here’s what fixed the problem:
Renaming “C:ProgramDataAutodeskApplicationPlugins” folder (this disables certain integrations)

Upon further investigation, I had to move the AutodeskSiteDesignerForRevit2015.bundle out of the ApplicationPlugins folder (in other words, delete it) to correct the issue. Then, I installed R2 (Autodesk_Revit_2015_R2.sfx.exe , Autodesk Site Designer (AutodeskSiteDesignerForRevit.msi), and UR5 for R2 (Autodesk_Revit_2015_R2_UR5.sfx.exe).

Here’s what didn’t work:

  • renaming uistate.dat
  • renaming revit.ini
  • renaming  “C:ProgramDataAutodeskRevitAddins2015.ren”
  • reinstalling Revit 2015 using steps below
  • applying RVT2015UR4.msp
  • uninstalling Dynamo
  • running Revit as Administrator
  • uninstalling Sundial and other Citrix Revit versions
  • renaming Revit program folder and Addins folder and reinstalling
  • making a new user profile

Reinstall steps:

  1. Uninstall Revit 2015 from Programs and Features in Windows
  2. Start Setup from your Suite media (in my case, Building Design Suite Ultimate 2015)
  3. You will need to input your serial number
  4. Ensure only Revit 2015 is ticked (gray tick), and do not install Service Packs
  5. Also untick BIM360 addin under Revit 2015 (if it finds a newer one the setup may fail)
  6. Untick BIM360 addin under Navisworks 2015 (if it finds a newer one the setup may fail)
  7. After Revit 2015 is installed, start it up to ensure activation is ok
  8. Install R2 (Autodesk_Revit_2015_R2.sfx.exe)
  9. Install UR5 for R2 (Autodesk_Revit_2015_R2_UR5.sfx.exe)
  10. Start Revit and test closing a file

How did this bug happen? I’m not entirely sure, but I think the number of  updates and the confusion around which UR5 update is for which Revit version may have resulted in Revit 2015 getting sad. But, its happy again now… and its a good lesson to remember the ApplicationPlugins folder when diagnosing Revit problems.

Something from the journal:
ExceptionCode=0xc0000005 ExceptionFlags=0x00000000 ExceptionAddress=000007FEFCDE940D 

Note: If you install the non-Subscription Update Release onto an R2 Revit, you will probably find that the nice extra things like Site Designer disappear. If this happens to you, reinstall R2 from the Subscription page and your new features should come back. The Autodesk_Revit_2015_R2_UR5.sfx.exe should hopefully not ‘break’ your R2 install.
More at:
http://knowledge.autodesk.com/support/revit-products/downloads/caas/downloads/content/autodesk-revit-2015-update-release-5.html

Direct link:
http://download.autodesk.com/SWDLDDLM/Updates/RVT/UR5/Autodesk_Revit_2015_R2_UR5.sfx.exe

Readme:
http://download.autodesk.com/SWDLDDLM/Updates/RVT/UR5/Autodesk_Revit_2015_R2_UR5_Readme.htm

Enhancement List:
http://revit.downloads.autodesk.com/download/2015RVT_RTM/UR5/Enhancements_List_RVT_2015_UR5_forR2.pdf

EDIT: More links from Revit Clinic:
Direct links:
Revit 2015 UR5
Revit Arch 2015 UR5
Revit MEP 2015 UR5
Revit Struct 2015 UR5
Revit LT 2015 UR5
Installation Readme files and Enhancements Documentation are available on each product page.

UR5 enhancements:
Improvements made in Update Release 5 build (20141119_0715):
 

Autodesk® Revit® Architecture 2015 Updates
Improves resolving of the Revit Server saved paths.*
Corrects the behavior of placing families in a project when the family type selector is expanded.
Improves stability when loading families that contain data created by add-ins.
Improves stability when ungroup a group.
Improved stability when filter a schedule.
Improved stability when opening projects with bad dimensions.
Improves stability when making edits in the Sun Settings dialog.
Improves stability when deleting parts while modifying division.
Improves stability when canceling new label creation in family environment.
Improves stability when editing materials in families in a workshared environment.
Improves stability when clicking the Macro Manager tool in the Family Editor.
Improves stability when multiple users load families and undo their actions in a workshared file.
Improves stability when two users loaded families of the same name.
Corrects an issue with ceiling-hosted lights that caused the lights to be deleted when the ceiling was moved or copied.*
Corrected an issue related to placement of face-based families on certain part elements.*

Autodesk® Revit® MEP 2015 Updates
Improves stability when editing a conduit temporary dimension in an elevation view.

Autodesk® Revit® Structure 2015 Updates
Improves stability when exporting multi-rebar annotation into DWG format.*
Corrects an issue with incorrect warning and error messages for groups in design options with a group containing structural framing elements or columns.*
Fixed an issue with the generation of the analytical surface for a vertical floor and slab.

Autodesk® Revit® API 2015 Updates
Allows the ability to offset the end of a wire when it is connected to other elements.

Why does this happen? Because the Bulk File Upgrader doesn’t work if it is trying to upgrade a Local and it can’t find a Central (I believe this is a Revit API thing)… and you may get this error:
filename.rvt could not be upgraded: The file-based central model could not be reached, because e.g. the network is down or the file server is down. 

The core problem here is that someone has probably given you a Local copy, when they should have given you a Central or Detached copy to link into your project.

If we want to upgrade lots of these “local-type” linked files, how can we get around this batch upgrade limitation? We will need to to use eTransmit – twice. Let’s say we are upgrading from Revit 2013 to Revit 2015:

  1. Make a blank 2013 RVT project
  2. Link in all the 2013 version files you want to upgrade
  3. Save the host file in 2013 and close it
  4. Transmit the host using Revit 2013, including Links and tick the ‘Open and Save models in the active version of Revit’ option (this places the newly saved linked models into a transitory state, where you can choose to save as central or work with this model temporarily)
  5. Open Revit 2015
  6. Addins – Transmit a Model
  7. Choose the output eTransmitted 2013 host file from step 4
  8. Make sure to tick the “Linked Revit models” and “Cleanup” boxes
  9. Click Transmit Model and wait for all of the files to be upgraded (yay)
  10. Remember to discard the host file before transmitting or copying the files

Note: using the “Add Files” option in eTransmit and adding RVTs manually will not upgrade them.

Here’s the link for eTransmit for Autodesk Revit 2015.

Also, you *might* have to press ok after each if you get this error (Easy Keynoter?)

On latest R2 version of Revit 2015, with Navisworks 2015 SP3 and Navisworks Exporters R3, there remains a Navisworks export bug that affects some projects after upgrade from previous versions of Revit.

Error: documented at http://knowledge.autodesk.com/support/revit-products/troubleshooting/caas/sfdcarticles/sfdcarticles/Error-No-suitable-geometry-found-when-exporting-from-Revit-to-Navisworks-2015.html

Workaround: You can use the selection method to Export and the error does not seem to occur:

  1. Open the 3D view to export 
  2. Select all visible objects 
  3. Go to Addins ribbon, 
  4. choose External Tools – Navisworks 2015 (Exporter) 
  5. In the settings, choose “Selection” (see attached screenshot) 
  6. Name the file and export as usual

Other suggested workarounds (did not work in this instance):

  1. Turn off Detail Items
  2. Try exporting again

or

  1. Remove View Template
  2. Set Level of Detail of view to something other than Fine
  3. Set Level of Detail of categories in V/G to the setting you desire (can be Fine)
  4. Try exporting again 

or
Try turning off categories one at a time to find out which Category the problem geometry resides in.

or
using “uncut” in the Family Editor to uncut the voids from everything, and then using ‘cut’ to cut them again. after reloading back through into the project, this also allowed the export to continue.

or
some other way…

      The log file reports:
      Autodesk.Revit.Exceptions.ExternalApplicationException: Object reference not set to an instance of an object.
         at Autodesk.Revit.DB.CustomExporter.Export(View3D view)
         at NavisWorks12.LcIRevitBase.Export3DView(View3D view_3d, StateDictionary state_dict)
         at NavisWorks12.LcIRevitBase.ExportDocument(String& return_message, ElementSet elements, LcIRevitParameters* params)

      Related forum:
      v2015 – Navisworks Can’t Import Revit – Autodesk Community

      It hasn’t shown up on Exchange yet, but it is already available for download on the Sourceforge page. There is an update to IFC 2015 (the one that is really robust, fast and accurate for Import and Export), and also some updates to 2014 IFC addins.

      Direct link to the MSI installer for Revit 2015

      Some of my testing:
      30% file size reduction in RVT when using Link IFC on 85mb steel model from Tekla v16.1
      v15.1.0 = 297mb
      v15.2.0 = 210mb

      66% file size increase in IFC when using export IFC to all proxies:
      v15.1.0 = 288mb
      v15.2.0 = 478mb

      Some key Export improvements from the readme (I’ve underlined points of interest):
      The functionality for creating and using user-defined property sets has been greatly enhanced. This includes:
      – Added a “DefaultUserDefinedParameterSets.txt” file to allow a user to create user-defined property sets for any setup, including the in-session setup.
      – Added the “IFC2x3 Extended FM Handover View.txt” user-defined property sets file to the installation. This also fixes a typo in the original version.
      – Allow the user to specify any file as a user-defined property set file, instead of being forced to use the default name and location.
      – Increased the types of fields that can be used from the original 4. The full list is detailed in the DefaultUserDefinedParameterSets.txt file.
      – The Setup dialog for the export alternate UI has been split into 3 tabbed pages to make it easier to find and understand the export options.

      – Significantly improve performance when trying to export a highly-tessellated geometry.

      New Import Functionality:

      – Add an “IfcMaterial” field that contains the material name(s) associated with the element.
      – Add an “IfcSpatialContainer” field that contains the name of the project, building, building story or space that contains the element.
      – Create multiple layers for simple cases of elements where IfcMateralLayerSetUsage is defined.
      Import IfcGrids. There are some fundamental differences between IFC and Revit Grids, most notably that IFC grids are per-view, and Revit Grids are per-model. As such, there may be cases where some grid lines show up in more views than initially designated in the IFC file.
      – Improve healing and logging of imported solid data that is slightly dirty. This should result in fewer missing objects.

      Import Bug Fixes:
      Fix “missing” faces when elements were cut by openings and the IfcOpeningElement sub-category had its visibility turned off.
      – Handle unbound circles used for profile definitions in certain cases.

      Heads-up https://twitter.com/digiacomoemma/status/517072219739291648

      My top three new features:

      • Revit 2015 Integration – export from Revit 2015, and easily load families straight into 2015 projects
      • keep your legacy content available for older projects while still being able to take advantage of new Revit features
      • Library Reports – export to CSV

      Tip: if you want to create a Saved Search for a given tag, use [tag name] in the Search term box. The square brackets tell Unifi to search tags.

      Release notes

      To learn more about Unifi, click the banner at top right or check out my previous post:
      New way to Share, Store and Search Your Revit Content

      Exact version number as of today v1.5.0.35051

      Interestingly, this hotfix comes in the form of a macro to clean up your files. The issue as stated on the Autodesk Knowledge Network is:
      In Revit 2015 the performance of some file is very slow. This means that
      opening material browser may take an extremely long time or Revit will
      hang. Typically you cannot execute the “Purge unused elements” command
      as well, because Revit will freeze. 


      Every time you edit a family and load it back in > overwrite > the
      number of materials will grow substantially. For example after 5 or so
      subsequent reloads in our sample file it jumps from 15551 to 186623
      materials.

      We have seen this most commonly when editing titleblock familes in the German and Japanese version of Revit. 


      Download the macro:
      DeleteStandardMaterials.zip

      Please go through the process below to clear out the extra materials:

      1. Close Revit.
      2. Extract the zip file: It will contain a DeleteStandardMaterials folder with two subfolders (AddIn + Source).
      3. Copy the AddIn + Source folders on the following path:
        C:ProgramDataAutodeskRevitMacros2015RevitAppHookupDeleteStandardMaterials
      4. Start Revit.
      5. Open the file.
      6. Open Manage/ Macro Manager/ Application Tab: The macro should
        show up in the Macro manager under application > macros as
        “DeleteStandardMaterials”.
      7. Select here “Execute” and start the command “Run” > This will delete Standard Materials.

      After these steps use Save As to save the file with a new name.

      Here are 2 videos showing the steps:
      https://screencast.autodesk.com/Main/Details/5bfa2fff-3443-45e0-a156-4c530c594c28
      https://screencast.autodesk.com/Main/Details/fb7eaa0a-b529-47b7-9e35-7d42c3944a0b

      Main page:
      File performance problem in Revit 2015 | Search | Autodesk Knowledge Network

      Heads-up:
      Be Revit – Do Family Planning: Revit streikt / Datei wird immer größer und reagiert nicht mehr?