I've been running it a little over a week now, and while I like it ok, I have yet to see a real advantage to using it over XP Pro SP2. My biggest gripe is that MS removed monitor spanning support so I can only extend my desktop to my 2nd monitor.
I will say that I haven't had any driver or program issues yet. My AV software works, nero works, and my printer works. I haven't tried out my scanner yet. Seems to boot as fast as XP, and I don't have an lack of resources, but I have a gig of ram too so that helps.