Mark Milian describes the best enhancement to iTunes one could ever hope for:
Music software has no way of knowing whether you like one song more than the previous, unless the user chooses to actively rate a track — thumb up in Pandora, 5-star picks in iTunes. Most people, I’d assume, don’t make the effort.
But you might find that many people, when they hear a song they like, will pump up the volume. Music services could listen to that, and take note for future instances of when it’s deciding what to play.
Do this, Apple. It would make iTunes loads smarter.