Organizing files and integrated video player
 

I think a system to organize files in the library (like in kazaa type programs) would be usefull.
You should be able to sort between audio files, video, images, software etc. You should also be able to organize files into categories such as bands or styles of music. That would just make it easier to find specific files a lot faster.
It would also be nice to add a video player as part of the program instead of opening up a seperate program such as winamp, quicktime, or windows media player.

This stuff would just make browsing and viewing/listening to files a lot faster and easier