I saw a demo of all the XGL stuff a few years back and was told it wasn’t quite ready for production yet… fast forward to present time, and now you can run it on Ubuntu!
You can download a free livecd to try out XGL here.
I tested it on a basic $300 Dell PC with a standard-PCI Nvidia FX5200 and it ran smoothly and perfectly without a hitch… most impressive… believe it or not, it may be more attractive than Apple’s Mac OS X…. Really! 😀