Hey Sindre,
I had been using KPlaylist for about 3 years before stumbling upon Subsonic as part of my "induction" into servlets and Tomcat in general.
This is one hell of a good build. I'm sure people have a wealth of feature requests and wants, but I am extremely impressed with the stability of the program, the layout, the extra information links and all the user rating/commenting abilities.
Superb work, keep it up!
Cheers,
Pete