Just did a test upgrade to iTunes 11 on a spare machine, and I'm glad I didn't do it on my real machine, as I'm not impressed by some of the changes.
I normally shuffle my music, so I have iTunes on the "Album List" view, and I have this displaying the play count, and last play date. The only way I can do this in iTunes 11 is to use the song view, which doesn't display the artwork. This seems a step back in my opinion.
The new Album view may look very nice, but it seems you have to click on each album to display it, and you can't customise it to display play counts and so on.
It seems a lot of people like this upgrade, and I've no desire to argue with them, but for me, I don't like the changes, and will be sticking with iTunes 10.