I installed it and now iTunes wont open. It just bounces in the dock 2 times and then stops.
I deleted the .plist files from the library. Still wont open.
Piff.
Start iTunes while holding the OPTION key.
If you did it correctly it will ask you to either select your iTunes Library or Create a new Library.
Try creating a new Library to see if you can bypass your problem. You can always import your media from your original library later.
Is iTunes 11.1 coming up tonight (after midnight)?