Mainboard: ASUS M4A785TD-M EVO, Socket-AM3 AMD 785G+SB710, DDR3, Firewire, GbLAN, m-ATX, HDMI, DVI, PCI-Ex(2.0)x16
Processor: Phenom II X3 720 Black
Power supply: Silver Power SP-400P2C 400W
CNet CWP-854 RT2561T D-Link G-520
The card is an integrated Radeon HD4200.
I tried the proprietary catalyst drivers from AUR, worked OK. Neverball was fast and xvinfo showed a buncha stuff wot I don't understand so that seemed to work too. I had to set TerminateServer=True to get kdm to not freeze on logout, as described in the wiki on ATI.
I switched to the free drivers, here xvinfo and glxinfo say "Error: unable to open display", but I can select OpenGL for compositing and get the wobbly windows etc. I'm not running KMS yet.
Problematic so far. See http://bbs.archlinux.org/viewtopic.php?id=89543