- Crossfading between tracks in the xine backend
- Get the analyzer to work on Windows with the phonon backend
- Double click folders in files tab to add them to the playlist
- Nicer error messages
- Copy/move files to the library (and rename them) from the files tab/playlist
- Configuration dialog for global shortcut keys
- Global shortcut keys implementation on mac and windows
- Save and load playlists (.pls) from files
- Buttons to shuffle and repeat the playlist
- Autocompletion from library when editing tags
- Edit tags inline in playlist view
- Menu item for adding internet streams by URL (maybe add them to the Radio tab too)
- More ways of sorting the library (by album, etc.)

Long-term:
- iPod/mp3 player support
- Automatic MP3 tagging from musicbrainz
- Album cover fetching from last.fm

Windows:
- Playlist delegates

Other ideas:
http://forum.kde.org/viewtopic.php?f=121&t=85039