The worst change, which completely breaks Apple’s set-in-stone UI convention, is the use of vertical close/minimize/maximize buttons. What were they thinking? If any other developer broke the Human Interface Guidelines like that, Steve Jobs would probably personally punch them in the face.

Astute iTunes users could point out the fact that when you used the “Mini Player” (Command+Shift+M) in iTunes 9, the same vertical buttons were used to save space. While that is true, it wasn’t for the main interface that you spend most of your time in. And such space-saving is only necessary in the Mini Player.

Anyway, I won’t bore you with further design ranting. You can restore the buttons to their rightful orientation by entering this command into the Terminal:

defaults write com.apple.iTunes full-window -boolean YES

Re-entering the command with NO instead of YES will reverse the change, should you take leave of your sanity in the future.