I'm running it on a 3 monitor setup and so far so good, I wish they had included the notification area on each monitor, so among other things I can quicky glance at the time and date no matter what I have going on, also the monitor edge triggers are pretty much shot on a multi-monitor setup.
Have they finally made it so that you can set per-screen wallpaper? I remember thinking that that was a really basic feature that was missing in win 7.
My video card driver allows it in Windows 7. The driver can also rotate display to portrait mode - one of these days I'll get a 3M monitor stand for that purpose.
screen http://i.minus.com/ibhcFWTFIYaO6d.PNG
Beyond all that the biggest issue with Windows 8 for me at the moment is that they didn't include the Windows 7 Solitaire games.