I've requested some of these, but at the iTunes music request page, so they've probably been ignored.
I'd like the option to 'always use crossfade' so that if you want to skip a track or choose something else during a party it will do so subtly.
I'd also like an option for when playing consecutive album tracks - 'ignore crossfade setting', although this might not work with the current gapped-playback system.
I like the links to the music store but does there really have to be so many arrows on the screen. How about if they were just in the artist column?
I'd like to be able to change my AirTunes speakers from the dock icon so that I don't have to bring iTunes to the front.
I'd like to be able to rate tracks with keystrokes like you can in iPhoto.
Intelligent track purchasing: if you've purchased an album, you shouldn't have to pay for the same tracks again when you want to get 'album only' tracks on a single. Same thing with buying singles before the album comes out. Make it easier to buy music spontaneously without the fear of being penalised after future releases.
Album notes for each track in the comments part of the audio file? Or a digital booklet with every purchase, so I can get the sort of information I would get from a CD? (and an elegant way of storing these in iTunes, ie, much more elegant than the current system).