One problem we encountered with development was Firefox's HTML5 <audio> not supporting MP3, so we have to use a flash player as a fallback for FF.
Hopefully we'll have a better solution for this in the future :)
Edit: This page has more info about HTML5 <audio> support: http://html5doctor.com/native-audio-in-the-browser/
http://www.mp3licensing.com/help/#4
(not saying you need a license, just pointing out that you might need to check)
One problem we encountered with development was Firefox's HTML5 <audio> not supporting MP3, so we have to use a flash player as a fallback for FF.
Hopefully we'll have a better solution for this in the future :)
Edit: This page has more info about HTML5 <audio> support: http://html5doctor.com/native-audio-in-the-browser/