when you guys say "AutoCAD 3D" are you refering to AutoDesk's relatively new Inventor Series(rev. 8 just showed up on my desk today) or the older, and very clumbsy) quazi-3D feature of AutoCAD (r14, 200, 2002 etc...)

If you have not tried Autodesk Inventor, you may want to try a demo, it is very nice and models parametrically in true 3D fashion. If you are familiar with Pro/E, it is very similar, but a little more user friendly and 10X less expensive.

Shaun