One small technical hitch that has not been mentioned: clicking the music note mutes the music, but it doesn't unmute the music when re-clicked. I think this has more to do with the current state of sound in C2 though.
I think it has more to see with the coding. (mute the music, go in a level, click the menu icon, come back to the first screen, music plays whereas it supposedly shouldn't.)
Anyway, the sound in C2 works. If anything it is the audio support in browsers that sucks.