I've been using Vitruvian for a few weeks now, here are my thoughts so far...
I've found a few problems, one was the textures weren't scaling properly. I sent an email to Vitruvian support and they fixed the problem the following week.
The other thing is that the PICTURE command in GDL doesn't export properly to VRML , at least in AC11. So the Picture 11 object or Carpet 11 object won't export the correct texture. I made a workaround by modifying the Picture 11 object to use material and texture commands instead of picture to map the texture.
The lighting is good, but there are no shadows as was mentioned before. The output is definitely better than the Archicad 3D window though.
The navigation is kind of tricky, it would be cooler to have an FPS game-type navigation like the AC 3D explore window. It is still usable though.
Everything else works as advertised.
If anyone has any specific questions feel free to ask.
cheers!