It would be great if multiple playlists could be supported similar to foobar2000, with tabbed browsing. I would probably not lose so many playlists if I could have multiple tabs of playlists open.
Basically any possible way to retain multiple sessions of playlists, (between application launches too) and the selection/scroll position within each playlist.
I have never been motivated to populate the 'library' unfortunately, for almost a decade now. But my Foobar2000, has tabs like 'Strauss', 'Boards of Canada', 'Jazz Funk', and some scratchpad playlists. I find it pretty productive.
And I am not the only one who's been spoiled by that feature of foobar, so it'll make it easier for some people to switch over when they realize xmplay has better stuff than foobar components