As a release of Firefox 4 Beta 9 approaches, Christopher Blizzard gives us an overview of what to expect. It is a nice laundry list of everything Firefox 4 will deliver when it is finally shipped to the general public.
Christopher’s list doesn’t quite separate what is new in Beta 9 though, but my understanding is that this release includes a number of updates to their HTML5 parsing & rendering by implementing more of what was once-known as Web Forms 2,
<video> preloading and buffering support fixes, and some fixes to pushState and replaceState.
In addition WebGL is now enabled by default, joining Chromium in an exclusive club of awesome. Opera and Internet Explorer have yet to ship a WebGL implementation but I suspect Opera isn’t far behind. Opera had previously shipped an implementation of WebGL’s little brother known then as 3D
<canvas> in a Labs build a few years ago.