The latest firefox 3 beta had a massive improvement over firefox 2 in regards to memory usage. It used 140MBs less RAM than firefox 2 in the tests Mozilla Corp ran. This is an improvement of 60%!
It’s edge over IE 7 was 400MBs – not really surprising considering Internet Explorer = fail. They also tried to test IE 8, but it just kept crashing (lol).
It’s edge over Opera was 20-155MBs. Not a lot, but still better, and especially a big difference on low-end machines.
Mozilla Corp says they fixed literally hundreds of memory leaks, thanks to community contributions. This just goes to show that open source software, is the BEST software!