..we're trialing Navisworks Manage from a city design perspective...exporting out from Autocad Architecture (with alot of property set data) and from 3dsMax (terrain). It's better than expected seems to have the ability to represent the data in Presenter>Rules in the same way ACA uses Visual Themes - so you can colour buildings according to their population, gross floor area, type of use etc based on data pulled in from the ACA objects. That's quite clever.
The rendering not a smudge on 3dsmax, things like mapping the bitmap to the terrain objects looks pig-ugly, there is no UVW-Mapping system per se ; you need to 'guess' where a bitmap starts, stops and what the rotation is. Also Navis doesn't pull in Vray materials from Max.
However the use Rules, as I said above, works ok and was an unexpected bonus.
We use tiny machines (6 years old running XP 32bit) but the model works fine on Navis...the same can't be said on ACA...it crashes the machine when all Constructs (or Xrefs if you like) are pulled in.
All round, ok experience so far.