OK, this statement really frustrates me, because it's so uninformed! What does iTunes 7 mess up when installed? Does it not run correctly before the repair? Of course it runs right! Check this out. I haven't repaired my permissions since I got my Mac, and I just did. Look at these log snippets:
I have removed the messages about correcting the problems.
Determining correct file permissions.
Permissions differ on ./Applications/iTunes.app/Contents/Frameworks/InternetUtilities.bundle/Contents/MacOS/InternetUtilities, should be -rw-rw-r-- , they are -rwxrwxr-x
...
Again, permissions issues in the modern OS X running recent software are rare, and permissions repairing will only fix a very small number of them. Sometimes it may actually set the WRONG ones, as in my iTunes example above: I had to manually change that InternetUtilities file back to be executable to allow that InternetUtilities bundle to work. After "repairing" permissions, it had acrtually made that program non-executable, which broke my AirTunes facility, and also my ability to access the iTunes store. So much for "Repair Permissions" fixing all my problems!
I find it truly ironic that a user complains of iTunes messing up permissions, only to find (myself) that I had NO problems before, decided to run "Repair Permissions" to see if iTunes had even modified permissions to something other than the receipt file, and the permissions repair friggin' BROKE iTunes' internet utilities, disabling my music streaming to my stereo!