The big feature being flipped on for the Firefox 22 Beta is full WebRTC support. WebRTC is the Web Real-Time Communication API drafted by the W3C and Google for handling browser-based VoIP, video chat, file-sharing, and other services native to the browser. There was already some WebRTC support in Firefox while now the support is fully-on.
Still coming to future versions of Firefox as it concerns WebRTC is TURN support for better connections, audio/video improvements, and Firefox for Android support.
More enhancements include support for the Web Notifications API, a new font inspector, other minor enhancements, and other bug-fixes.
Additional details on the changes to find with the Mozilla Firefox 22 Beta can be found out from the release notes.