I'm very excited with 3D desktop after watching AIGLX and XGL in action with beryl or compiz window manager. I haven't been able to get it run on my computer with my video card since it is not supported composite extension and DRI simultaneously. The ATI's proprietary driver (fglrx) I use, doesn't support dri and composite extension simultaneously. I downloaded kororaa live CD to try it out and I was amazed.
At one point, I downloaded xorg, compiz and Mesa from cvs and I managed to get Xorg compiled with Xgl enabled but I couldn't get compiz to run because there was no composite extension.
Picture above is a screenshot of my desktop running dropline GNOME on Slackware and Xgl running in a window with KDE as the window manager. It's like running X in X or nested X.
However, I'm still trying... :)
Xgl,compiz and Mesa - http://www.freedesktop.org/wiki/Software_2fXgl
Dropline GNOME - http://www.droplinegnome.org/