I'm curious about this too. My only gripe with third party music apps is that Apple won't grant them access to features I use regularly. The most important two for me are:
1) ability to update play counts/history, and
2) ability to rate songs (I have a small but significant # of songs that need rating)
In each case, these two help me manage my large library since smart playlists regularly cycle songs in and out based on these criteria.
My two biggest wishes that would make the stock app useable (for me) would be:
1) Artist->Album wouldn't show all songs, and
2) Sort Albums by Title, instead of chronologically [or at least a) give the option to toggle the sorting, or b) allow me to edit the year used since they are often based on remaster date, not original release date, making the listing seem random if you know the catalog well.]
I've already sent feedback.