The closest thing I can think of right now is using an external player such as Foobar or Songbird for the playback of music, instead of the embedded Flash player.
The only "desktop client" that I'm aware of is a project by my friend mang who wrote this:
https://github.com/mang/mpdc#readme. It doesn't even require Subsonic to run, it just uses the MusicCabinet database to create artist radio playlists etc.
I actually wrote an iTunes plugin a while ago (which only works on MacOSX) that adds the artist radio, genre radio, related artists etc as new menu items inside iTunes, but it doesn't work straight out of the box. but here's the code anyway in case somebody wants to fiddle with it (it does require some coding skills though and it's not up-to-date, so it's more conceptually interesting):
https://github.com/hakko/iTunes