Played with Windows 8 on a VM a few weeks ago... I can't stand it.
I'm a huge champion of Zune and it's UI, but I can't deal with the similar interface being applied to my entire desktop. I opened some app and I couldn't instinctively figure out how to exit the app - I think I clicked on various things and entered some key combos. I still can't remember how I closed the app (Windows key I think?)
For a pure tablet experience, I think the OS could work... but I wouldn't consider putting it on my convertible laptop tablet that has a touchscreen.