A week or so ago I updated the linux build of the gstreamer based HTML5 video implemention with some fixes that make it work nicely with the public sites using <video>. This includes wikimedia and metavid. Video's on those sites with that build show a much better user experience than previous builds.
Two new backends are in progress by other Kiwi Mozilla team members. A DirectShow backend for Windows being developed by Chris Pearce and a QuickTime backend for Mac OS X being developed by Matthew Gregan.
The git repository is based on regular imports of the Mozilla CVS repository. This repository tracks Firefox 3 which is close to being released so updates to CVS are few and far between. The video/audio work will not be in Firefox 3. The plan is to have them in a release soon after, scheduled for around the end of the year. If all goes well this will have backends for gstreamer, DirectShow and QuickTime for the relevant platforms.
The Mozilla repository for this release is currently a Mercurial repository called mozilla-central. I've not yet migrated my work over to this repository but will do so soon. My Firefox git repository now has a branch containing a regular import of the mozilla-central mercurial repository. Moving over to mozilla-central should just be a simple case of merging that branch into the video work.
The bugzilla bugs with the patches for this work will be updated in the next day or so. I wanted to get the refactoring for the <audio> element done before updating them for review.