one huge annoyance for me was when i plug in the ipod, it would bring the update dealie in iTunes to the foreground (pulling focus away from the library). That part was understandable (though I'd've like to be able to not have it focus, and still update the ipod). But, what was really annoying was, when it did it I would hit command-L (to bring focus to the current song, therefore putting me back into the library). When the ipod update completed, it would rip me out of the library view and push me right back into the ipod view. used to really piss me off.
as for features, i would like for iTunes to have some kind of icecast streaming possibilities. DAAP was really cool, while it lasted, but icecast would be better. Then I'd be able to listen in at work on a peecee, or anywhere for that matter, since icecast clients already exist (for nearly all platforms). I don't know a huge amount about icecast, but i think it allows the client to selectively choose tracks, which would be preferable. But I'm fairly certain that it allows streaming of a continuous type. So, in theory, itunes could icecast stream its current playing music, which would be sufficient. It would also be useful, or so i would think, for the limited purpose of synch'ing music. My roomies in college and I would have a lot of the same music, often playing unharmoniously, and it would be cool if they could all synch into a stream I (or someone else) sourced, and the tunes could play through all our speakers simultaneously. I was also thinking that such a thing could be setup in offices as a PA replacement/alternative. At work when ur not at ur desk, and someone tries to call you, they'll often then hit into the PA and say "so and so, please call xxxx." the PA speakers are in odd places though, and I would almost never hear them. Everyone has speakers on their comp though, and this streaming thing could be useful there (well, not at my job actually, since we dont have any macs, but in theory for a mac-based office).
i also think it would be really keen if itunes had some kind of user controlled manner to select the next 'random' track. itunes isn't random enough for me. but if they allowed an applescript, or a shell script, to access the list of songs, and meta data, i could make it select songs that haven't been played in a while. or i could make a version that would tend to stay within a genre, or all kinds of possibilities.