To contribute my experiences:

No problem getting it to work under Vista. I didn't run any benchmark tests, but it seemed snappy. Installed SP1 RC1 with same results.

Under XP, had to slipstream the ICH9R drivers, no other problem. Install time around 10 minutes with a Raptor RAID, so I don't think there are any major problems here either. (The Vista sound stuttering issue was worse than ever on this board, and I didn't feel like fighting with it all over again with class starting back up tomorrow! SP1 doesn't fix this...)

With a Highpoint RocketRAID 1820A card installed, the RAID on the ICH9R is not an available option in the BIOS boot menu. There may be a way to change this, no idea. With two other hard drives attached to the ICH9R while it is in RAID mode, they do not show up as boot options either (with or without Highpoint card). The optical drive attached to the ICH9R appears as an option in both cases.

This board is very finicky about what's attached to it, for example with my USB hub attached the pre-OS boot process takes about 5 minutes. Also my generic SI SATA card doesn't function properly on this board, boot stalls on it while detecting drives - but if you power up the drives after boot, it works fine, and it works fine on another mobo. The version of the Asus software package that comes on the CD also caused major issues in Vista. Good hardware, substandard software? :/