From the "under construction" files:

Mozilla developers have pushed out their latest milestone build for Firefox 3.1 with the alpha 2 release. Surprisingly though, this latest build does not yet include the faster Tracemonkey JavaScript engine which Mozilla developers are claiming is faster than Google Chrome's V8.  Tracemonkey is however in the nightly builds of Firefox 3.1 and there are instructions for those that want to play around with it.

For me in my narrow world view - Tracemonkey is a defining feature of Firefox 3.1 and will be criticial to Mozilla's positioning versus Google Chrome (and other browsers) in the newly re-invigorated browser wars.

That said, Firefox 3.1 Alpha 2 has made some other interesting improvements, among them is the ability to drag and drop tabs between browser windows (and yes I know - Chrome does this too). There is also support for the HTML 5 <video> tag which one day will make embedding video a whole lot easier than it is now.

The other interesting item is somthing called Web Worker threads - which is supposed to be an approach to moving compute intensive threads to a background process. It's an interesting idea and offers the intriguing prospect of limiting the impact of JavaScript on page performance.

Clearly there is alot more work for Firefox 3.1 to come, but the latest alpha is still the next step over Alpha 1 which came out back in July.

As to when Firefox 3.1 will actually be ready for prime time - that's an open question that Mozilla's schedule is still leaving open.