It seems odd to me, though, that all of a songs (Is) metadata (the correct word?) other than its Prefs > Options > Equalizer Preset and, I think, Volume Adjustment are attached to its file in ~/Music/iTunes/iTunes Music and can be easily restored, while the only way to restore equalizer and volume settings appears to be by importing an existing ~/Music/iTunes/iTunes Music Library.xml (Edit: or is it ~/Music/iTunes/iTunes Library, or is it both) file (as opposed to populating [a] new one[s]).
The rationale there is that the "info" part (such as artist, album, song, composer, year) consists of fairly objective qualities, set in stone by nature... whereas the "options" part (like EQ, vol., start/stop times, and ratings)
could be viewed in a more subjective light, wherein different users might desire different values.
As far as the other thing goes, iTunes can (presumably) work from either equally well... whereas the XML file is more easily understood by 3rd-party wares. [it might/could also serve as sort of a "safety/temp" backup, while iTunes writes out its frequent updates to the binary version.]
