I use Amarok for my music needs. The feature I enjoy most is the Now Playing playlist in a split window with my music library. I can add whole playlists, whole albums, whole discographies, or just individual songs.

Another feature I would like to see is some sort of network control... I am frequently on the couch with my laptop, and my desktop is playing music. Or my roommate wants to queue up a song. What I finally did was use Amarok and VNC (with a java web client) to let anyone log in and update the playlist...)