Do you ever struggle with lines jumping around at extreme zoom levels, or weird numbers appearing when you are using many decimal points in your dimensions (like 1000.0000034)? This may be why:
Revit uses double precision numbers for all calculations (as do all CAD systems), and they are only good to around 14 or 15 digits.
(the above post was by irwin, Revit Founder)
Other programs allow more decimal digits but they do try to fake (unsuccessfully) more precision than they can really provide.