Few bugs from twiddling with it a little bit, and this probably only applies to lesser known artists too:
If the songs have been scrobbled but aren't actually ON last.fm, the tracks don't work.
If a track doesn't play for whatever reason after you've clicked on it, the finding video filter comes up again, making the background increasingly impossible to see and locking you out of making a different choice. Might be worth giving that a work around.
Other than that, still a crazy good 'game' or whatever it is.
Complete genius. How this hasn't been done before I'll never know. I think the GUI does need a lick of paint, but frankly, who cares how it looks when it actually works better than last.fm (not saying much but hey)
 "Music Quest"){kind=icon}
 "Epic Combo!"){kind=icon}