i was planning on using unity on my (recently and very cheaply purchased) WeTab, but i changed it back to my customized "desktop" edition (stock gnome with touch-friendly icons and controls) quite soon.

the biggest problem i had with it is the integrated menubar. i really hate that it may make sense on very small screens, but it's really annoying when you want to have several windows open.
the dock on the left side is nice, but i still prefer the combination Cairo+compiz.

IMO, unity still has a long way to go. it's to soon to make it the default WM.