I ran the tests on my Ubuntu 10.10 laptop running Firefox-4.0 Beta8pre and Chrome 9.0.570.0 (64571) and Firefox actually beat Chrome 2943 to 3645 (or a 23% improvement) averaged over two runs.

Gotta love browser competition!

don't ever average software benchmarks, it doesn't make sense. always take the best run.

Err, your last sentence is a bit weird. First of all, 3.6 already has TraceMonkey; what's new in Fx 4 is JägerMonkey, and the integration between it and TM. Second, the Mozilla JS engine is largely developed separately (all of the actual development these days is in a separate repository, which merges semi-regularly with the main mozilla-central repo), but have you seen any other browser backporting anything other than security fixes?

Huh... I haven't heard anyone in the Mozilla world even talk about backporting to 3.6 (even to say it's a bad idea). Everyone is very focused on 4.

I'm very happy with the result. However, on some javascript intensive webpages, such as https://console.aws.amazon.com/s3/home, it hangs the whole Firefox for a little while. Hopefully with a long timeline to the release, no such issues remained.