I have quite a few playlists as tabs but as the list gets longer and longer, I still use the sidebar or playlist manager for accessing the rest of my playlists. It got me wondering why there's no way to rearrange the order of playlists either in the sidebar or the playlist manager.
Something I also think would be great is an option to create a blank space to go between playlists (or certainly between smart and normal playlists etc). Visually, it's a small touch but makes for faster and easier recognition of what playlist you want to use.