i have a G4 powermac 933 mghz with 1.25gb ram :) and geforce 4 mx :) (screen resolution 1280*1024)
i just tried the user switching.
acount x- apps open: dvd player playin 'the time machine', ical, isync, iphoto, and other apps....
i switch to acount y and the cube effect is very smooth...