I'd like to be able to move songs from one playlist to another. When I come across something I want to check out, I add it to a "Stuff to check out" playlist. Then when I listen to it, I add it to a "Not good" or "Meh" playlist, or add it to my collection. When doing this it takes 2 steps - 1) add to new playlist, 2) remove it from current playlist (and I have to do this just before the song ends as I always listen on shuffle, and sometimes going back to previous song messes things up!). So just being able to do this in one step would be a nice convenience: Move song to playlist --> Playlist X.