It Just Works! Graphics with Beryl, sound out of the box, network out of the box (no wireless with wpa, but otherwise it Just Works, and I’m not using wireless on a desktop, especially when I have dual Gigabit ethernet). Using my Samsung LCD TV also worked out of the box (after I managed to actually hook up the last power supply cable, which I’d forgot…)
Installation of Ubuntu Feisty Fawn had no hitches at all. Only thing that doesn’t work is lm-sensors, due to it (monitoring for ASUS P5B/Dlx mobo) not being supported properly in the current Feisty kernel. Gkrellm does work though. So gpu and hard drive monitoring works using gkrellm. I’d really like to have the sensor-applet work, but this is definetely minor.
The most important thing is: my first real attempt to build a computer works!