In Firefox 3.6 and 4 beta 6, audio no longer works since revision 2f23d6f.
Underlying cause of this seems to be Audio#canPlayType telling us Vorbis is unsupported (returns empty string) when invoked too early. SoundKit currently calls this on document loaded.
(Manual invocation from the console later during play returns 'probably', which is correct.)
Fixed in Firefox, but apparently now broken in Opera. grumble