I still have a love-hate thing going on with iTunes 11. I just don't find the interface as intuitive as the old one and the search function drives me batshit.
If you have a sufficiently large music library, don't even think about entering a search that begins with "the." It'll choke everything. And when you do get the result you want, I always end up clicking in the wrong spot to get to where I want to be.
Maybe it'll be better with v11.0.2, which was released yesterday. Along with a bunch of bug fixes, there's a new "Composer" view (good for people who want to search by songwriter) and improved playlist response--whatever that means.
I haven't played with the new version yet--I'm currently updating my iPhone and iPad to the new iteration of iOS 6--but I'd be interested in any, er, relationship issues you have with iTunes 11.