Peter Cohen, in a column for iMore:
The net result is that iTunes does a lot of things, but does them poorly. The interface has become needlessly complex, and attempts to refine and improve it have largely failed as a result. iTunes is the one Mac app that drives your experience with music, downloading television shows, movies and apps. It’s trying to do too much. It needs to do much less. As a result, even the name “iTunes” has lost its meaning – “tunes” are only a small part of the app’s overall function.
I won’t ever argue that iTunes works flawlessly for me, but I rarely run into any major issues, even with my large library. But, then again, I also don’t use iTunes Match. iTunes on Windows is appalling, however; it’s the biggest complaint I hear from my Windows-using friends.
As I’ve previously argued, though, I think the monolithic iTunes design makes more sense than using separate apps for purchasing, playback, and syncing. When it works, this experience is more seamless and less convoluted than purchasing a song in one app, adding it to a playlist in another, and then selecting that playlist to sync in a third app. But we’ll see how this plays out this autumn; Mavericks includes iBooks, an entirely separate store application.