Rivals iOS 6 Maps for reputation damage capability
OK, there are no bendy bridges or misplaced zoos, but this app is at the core of Apple's business model and this upgrade drops useful features (http://news.cnet.com/8301-13579_3-57556548-37/7-features-apple-killed-off-in-itunes-11/) and contains at least one terrible bug (https://discussions.apple.com/message/20430860#20430860)
No Coverflow - bit of a backward step visually
No iTunes DJ - my favourite way to get a controllable but random playlist is gone
No option to set gapless playback - when you want that, you really want it.
Fail to update play count or last played time - fail, even if there is a sort of workaround.