[Niten]

I'm comparing to Firefox 3.6; Firefox 4.0 isn't released yet. But everything I've read indicates that Firefox 4.0 will still have a single-process, non-low-integrity process model, with all the security and reliability implications that go with it.

Hopefully Firefox 4 will catch up to the likes of Chrome and Safari (and IE 9) in terms of JavaScript performance, judging by benchmarks on the release candidate, but I haven't seen any indication that it addresses Firefox 3's fundamental design weaknesses. Of course, feel free to correct me if I've missed something in the release notes somewhere...

[Legion]

Understandable, but still, when it comes to comparing how IE 9 stacks up to "Firefox" on rendering engines and memory usage, it doesn't seem particularly meaningful to compare the brand new IE 9 to the old Firefox just because IE 9 released a single week before the next major revision of Firefox is slated to. Not that you were writing a New York Times article here or anything. :)

I certainly understand your other point about the single-process design.