My top 4 new features / changes in Revit 2015:

  1. Sketchy Lines!
  2. IFC Link
  3. Revision cloud arc length (ie. “Revision Improvements”)
  4. “Username has been updated to match Autodesk 360”
http://lumion3d.com/

Official page for Revit 2015 new features:
New Architectural Design Features | Revit Family | Autodesk

If you want to talk about Revit 2015, your expectations and the new features in general, check out this thread:
Today is the day!

Steve’s post:
Revit OpEd: New Feature List for Revit 2015

Sean’s posts:
What’s new in Revit 2015 | Paradigm Shift
and system requirements, including running Revit 2015 on a Mac

Chris’s post (some valuable commentary here):
Revit Rants: Revit 2015

John Flanagan’s post about Sketchy Lines:
Revit Architecture 2015 – New Features – Blog – CADline Community

Oliver describes the new exp and ln functions before they are even listed in Help:
at this link

 Steve also discusses them here.

Lejla’s top 5

Structural enhancements like Justification Points, more info at:
Revit 2015 – Structural Framing Enhancements | Autodesk Revit Structure

Structural reinforcement for Parts:
Ideate Solutions: Autodesk Revit Structure 2015: Reinforcement for Parts

To learn more about Sketchy Lines, check out:
RevitCat: New Sketchy Lines in Revit 2015
(Tim recommends setting both sliders at 3 and starting from there)

 
David Light also posted about Sketchy Lines at:
Revit : Revit 2015 – sketchy lines

More on the schedule changes:
RevitCat: New in Revit 2015 – Schedules & Parameters

Dan Stine’s post (It includes some detail information on the Hidden Lines changes in Revit 2015):
http://www.aecbytes.com/tipsandtricks/2014/issue70-revit.html

Revit Structure 2015 showing Rebar improvements, by Lawrence:
Revit Structure 2015 – New Reinforcement Tools | Autodesk Revit Structure

To find out about performance enhancements in Revit 2015:
Revit : Faster….Faster…..Revit 2015

Perfect Project (Russian blog) has a very detailed post, mentions the Image Type parameter for families.

Russian forum post, with details and lots of screenshots. eg number of filters increased to 8 in schedules, labels in 3D views react to changes more predictably.


In Russian, forums.autodesk.com/t5/Revit-Русский/Новые-возможности-Revit-2015/m-p/4925120
Translated version

Suite changes and updates:
Autodesk Unveils 2015 Suites for Building and Civil Infrastructure Industries
including a few downloads like

Download Building Design Suite 2015 backgrounder
Download Building Design Suite 2015 backgrounder
Download Building Design Suite 2015 backgrounder
Download Building Design Suite 2015 backgrounder

http://inthefold.autodesk.com/files/building-design-suite-2015-backgrounder.pdf

Redstack page:
New Autodesk 2015 Design Suites

Another nice summary:
Top Reasons to Choose Autodesk Revit Architecture 2015 | CADD Microsystems 

Lot’s of new features pages for different Autodesk 2015 products at:
Cadline Insider Blog – Cadline Community

AutoCAD 2015:
AutoCAD 2015 in two minutes | CAD Panacea

Inventor 2015:
Autodesk Inventor 2015 Released – Whats New? T-Splines? | Design & Motion

Here is what the new Revision Cloud tools look like:
via
Today is the day! – Page 4
Ben also re/posted a few videos demonstrating Revit 2015 features.  I have started a video playlist of these, and also added a summary of Revit LT 2015.  I will add to this playlist as further videos become available.  It is embedded here:


Some good informational videos from the Revit 2015 help site
New In Revit 2015
New Feature Videos 2015
via The PPI Group Blog: New Feature Videos – Revit 2015

Also:
 
What’s New in Revit 2015 and Related Autodesk Products from Alfred Huang on Vimeo.

EDIT apparently some of these links are broken. I will look into this. In the meantime, you should use the Virtual Agent if you want to download.

Revit 2015 direct download links:
Onebox
http://trial.autodesk.com/SWDLDNET4/2015/RVT/DLM/Autodesk_Revit_2015_English_Win_64bit_dlm.sfx.exe

RAC – Architecture
http://trial.autodesk.com/SWDLDNET4/2015/REVIT/DLM/Autodesk_Revit_Architecture_2015_English_Win_64bit_dlm.sfx.exe

RST – Structure
http://trial.autodesk.com/SWDLDNET4/2015/REVITST/DLM/Autodesk_Revit_Structure_2015_English_Win_64bit_dlm.sfx.exe

RME – MEP
http://trial.autodesk.com/SWDLDNET4/2015/RVTMPB/DLM/Autodesk_Revit_MEP_2015_English_Win_64bit_dlm.sfx.exe

LT – Revit LT
http://trial.autodesk.com/SWDLDNET4/2015/RVTLT/DLM/Autodesk_Revit_LT_2015_English_Win_32-64bit_dlm.sfx.exe

AutoCAD 2015:
http://trial.autodesk.com/SWDLDNET4/2015/ACD/DLM/AutoCAD_2015_English_Win_32bit_dlm.sfx.exe

http://trial.autodesk.com/SWDLDNET4/2015/ACD/DLM/AutoCAD_2015_English_Win_64bit_dlm.sfx.exe

Navisworks Manage 2015:
http://trial.autodesk.com/SWDLDNET4/2015/NAVMAN/DLM/Navisworks_Manage_2015_dlm.sfx.exe

Navisworks Simulate 2015:
http://trial.autodesk.com/SWDLDNET4/2015/NAVSIM/DLM/Navisworks_Simulate_2015_dlm.sfx.exe

Release dates and product keys for 2015 products can be viewed at:
» 2015 : Release Dates, Product Keys Tech Solutions
(the release date listed for Revit products is 11 April 2014)

Building Design Suite Premium 2015 (recommend that you copy/paste these links into a good download manager, like Free Download Manager Portable):
http://trial.autodesk.com/SWDLDNET4/2015/BDSPRM/DLM/Building_Design_Suite_Premium_2015_English_Win_32_64bit_dlm_001_003.sfx.exe
http://trial.autodesk.com/SWDLDNET4/2015/BDSPRM/DLM/Building_Design_Suite_Premium_2015_English_Win_32_64bit_dlm_002_003.sfx.exe
http://trial.autodesk.com/SWDLDNET4/2015/BDSPRM/DLM/Building_Design_Suite_Premium_2015_English_Win_32_64bit_dlm_003_003.sfx.exe

If you want to get Revit 2015 right now (in March 2014), you can install Infrastructure Design Suite Ultimate 2015 from these links:
trial.autodesk.com/SWDLDNET4/2015/IDSU/WI/Autodesk_IDSU_2015_English_Win_64bit_wi_en-us_Setup.exe
or
http://trial.autodesk.com/SWDLDNET4/2015/IDSU/DLM/Autodesk_IDSU_2015_English_Win_64bit_dlm_001_004.sfx.exe
http://trial.autodesk.com/SWDLDNET4/2015/IDSU/DLM/Autodesk_IDSU_2015_English_Win_64bit_dlm_002_004.sfx.exe
http://trial.autodesk.com/SWDLDNET4/2015/IDSU/DLM/Autodesk_IDSU_2015_English_Win_64bit_dlm_003_004.sfx.exe
http://trial.autodesk.com/SWDLDNET4/2015/IDSU/DLM/Autodesk_IDSU_2015_English_Win_64bit_dlm_004_004.sfx.exe

Some other download links:

DWG Trueview 2015
http://download.autodesk.com/esd/dwgtrueview/2015/SetupDWGTrueView2015_ENU_64bit.sfx.exe