I had some issues with my ati 2600 xt, WMP12 freezes when in dual monitor mode.
but i was using beta drivers back then so i think it should be sorted by now, other than that no problems with 32bit.
the one thing i really miss is the on the fly audio switching, i can switch between pc speakers and hdmi without having to play the video/music again unlike vista.
RC1 should be out officially on May 5, can't wait to make it my default OS.