Finally got around to trying out Xgl on Wednesday. Used the xgl-coffee overlay (link to HOWTO) and modified ebuilds to be live cvs instead of dated snapshots, so I don’t need to ever bump them. You can get the new ones from my overlay if you want them — x11-base/{xgl,xorg-server,x11-drm}, x11-wm/compiz, x11-libs/{cairo,libdrm}, media-libs/{glitz,mesa}, x11-drivers/xf86-video-ati will get you basically the latest X there is.
After fixing an accidentally applied aiglx-only patch that made all the pixmaps upside-down in compiz, stuff worked quite well on my iBook G4 (Radeon 9600 or so).
The motivation for doing this was a demo to my LUG at the meeting. I also gave a 5-minute talk on how to get involved in open source. I’ve posted the slides [PDF], but they’re quite unhelpful without me narrating.