Strange. Concerning the double playback, the only this I have noticed that the previous track can play for a short while when changing track, this due to some latency with pulseaudio. Issues with the library are difficult to fix on N900 as it is not possible to update to the latest version (which is in use on the N9/N950 QSpot version). Some of the problems (e.g., playlists not showing up before restart of QSpot) is definitely libspotify related.