I'm using a P5B-D in a dual boot setup with XP and Vista Ultimate. Vista recognised all of my hardware (no F6 drivers needed) including sound, amazing!
From my experience the Vista HD audio driver is better than Analog Devices' own effort (which are WHQL and available from
http://support.asus.com). I have headphones/mike plugged into the front panel and use the S/PDIF optical out to an amp. The Vista drivers recognised both the amp and headphones while the SoundMAX drivers thought the headphones were speakers.
I also have a problem with my 7900GTX, the Nvidia drivers are not up to scratch and only offer basic support for Vista. Games seem to be fine (2142, HL2 etc) but if you want to use Dualview (and in my case Media Centre on an HDTV at 1920x1020) forget it.
The worst thing is that the generic Vista grahics driver is great for dualview! All resolutions for my HDTV are recognised and Media Center works perfectly, the only downside is that games suck, (unplayable due to tearing) typical! I found myself using the Nvidia driver for games and rolling back to the Vista driver if I wanted to use Media Center, which caused problems in itself.
I'm now using XP for everyday use untill Nvidia sort their act out