I installed Ubuntu 7.04 last night on a Windows XP host. I assigned it 1 gig of RAM and 64 megs of VRAM - runs beautifully.
When I tried to enable Compiz, all I got was a white screen (which reverted to normal after about 30 seconds. I assume you have to click 'okay' to confirm like when you're changing the resolution settings in Windows).
Has anyone got it running successfully? Any tips? Thanks!