On August 21 "we landed TraceMonkey in the Firefox 3.1 development tree, configured off by default. We have bugs to fix, and an enormous number of optimizations still to choose from, but we're charging full speed ahead on the work we need to do for this to be a part of Firefox 3.1. Depending on the benchmarks you choose, you might see massive speed-up, minor speed-up, or maybe even some slowdown - those latter cases are definitely bugs, and reporting them through bugzilla will be a big help," Shaver stated.
Firefox 3.1 Alpha 1 for Windows is available for download here.
Firefox 3.1 Alpha 1 for Linux is available for download here.
Firefox 3.1 Alpha 1 for Mac OS X is available for download here.