I am not sure about the 2010 release, but 2009.1 would not read a native Revit file. You have to export
the Revit file, for Navis to read it correctly.
It took me some doing to get things to read correctly and who up as solids in Navis.
It's not as plug-n-play as I would have thought it would. My situation was a little
unique as I was working with 2004 file format.
I use navis Review for everything I did. I could not afford Navis manage which includes the Clash Detection.
They conveniently put the most desired option in the most expensive variation of the software.
Honestly, Navis Review is worth it's weight for what I need it for. If you are trying to avoid things,
you can visually see if you are hitting something or not. I was only running conduit. HVAC would be a lot
harder to do w/o clash detection to automatically check.
The other issue that you will/may have is point of origin. In my opinion, it is much easier to make the
origin the same between all files. With Civil, this is probably not an option. Internal to Navis, you do have
the ability to move things around to make them have a point of origin. You also have to watch scaling.
If one file is in decimal and another in architectural, they will come in at different sizes...
Pieter