I use
Synergy, and its well worth the $5 I paid for it (gone up to a still reasonable $7 now). What I like about it is the option to switch playlists from that without going to iTunes, I like the way I can have a floater come on the screen when the track changes (with a little preview of the album cover, and my rating) so I know whats going to be played.
I also like the ability to add keyboard shortcuts for most features in iTunes - I have ctrl+cmd+up to increase my rating, ctrl+cmd+down to decrease my rating, ctrl+cmd+left to skip back a track, and ctrl+cmd+right to skip forward a track.
Download the demo and try it!