I don't know much about the audio situation, but it cannot be more dreadful than appcache.

Mozilla is actively working on implementing the Web Audio API (originally introduced by Chrome), which should make it simpler to write cross-browser audio code. Large parts of this work have already landed in Firefox Nightly builds: https://bugzilla.mozilla.org/show_bug.cgi?id=779297

I had thought the same thing too, but after updating our app to a mobile web app, we found there are many out of the box solutions that make audio work across various platforms and browsers.