Features in KDE Base
Houston, we have MPRIS support!
Tested with Audacious 1.4.4. The only bit that doesn't work is the track number - Audacious doesn't export the track number via the GetMetadata() method of the /Player object, and it's difficult to deal with the /TrackList object at the same time due to the silly MPRIS convention of giving different interfaces the same name...
Next stop, extragear! (And XMMS support, of course.)