If you've tried re-installing iTunes 10.7 under the release version of Mavericks, using guides that were developed for Mountain Lion and before, you may know by now that doing so messes up the operation of the Mac App Store (MAS). iTunes 11 now shares the use of several important frameworks and libraries with the MAS, and if you do a full install of iTunes 10.7 in Mavericks using Pacifist, you'll end up with a less than functional software update system (it should be noted that this has been reported to only manifest itself after the first post-install reboot). Because the MAS is now the delivery mechanism for all Apple software, not only applications but system software and security updates, it's no longer feasible to consider re-installing iTunes 10.7 using the standard methods. To avoid this problem, I started to wonder whether it was possible to re-install iTunes 10.7 by simply extracting iTunes.app by itself, without overwriting any of the other support components. I can report that I was able to do this with success, there being only a few caveats: (1) You'll need to rename iTunes.app to something like iTunes10.app. The reason for this is that if you leave the name the same, and you ever repair permissions, disk utility will mess up the permissions of the older version of iTunes and it won't start, because it will be assuming that the app is version 11. Renaming the app makes it invisible to permissions repair. (2) In order to prevent from accidently starting iTunes 11 and permanently converting your library indexes and playlists to the version 11 format, rendering them unusable by iTunes 10, you should rename the version 11 app to ".iTunes.app". Notice the period at the front? That makes the app invisible in the Finder, and prevents it from showing up in Spotlight searches. Now, if you ever do decide to use 11 for whatever reason, the app is still there, so you can always rename it back, but it's out of the way, and it's impossible for you to invoke it by accident. (3) When first starting iTunes 10.7, you may get a message saying "an unknown error occurred". You can safely ignore that. Everything seems to be functioning correctly, although I don't have an iOS device to test syncing with, and if you're using iOS 7 on any device, syncing would require iTunes 11 anyway. Let me know if anyone else tries this and if you have any problems. TL;DR Full re-install borks MAS in Mavericks, so extract app only and rename.