I have been using the N900 version of QSpot today(1.2.0-1), and have still not experienced any issues. Have tried to switch tracks quickly, change playlists, play albums, etc. and everything seems to work, Surprised that the audio quality is really amazing on the N900, would say it beats the N950

Are you using some custom kernel / configuration? It seems strange that two tracks could play at the same time, as only one audio buffer is used internally.