Looking at gentoo-wiki.com
it seems that 7900gs is almost the only one not supporting XGL. I am an unlucky one that bought Dell 9600 and not only, also with this card! (I am unhappy not being able to overclock the machine....)
I tried to activate 3d in OpenSUSE that now finally support this really good and usefull Cube effect.
Why this? Or is there a solution?
(I installed the latest drivers today from the NVidia site...)