Firefox 3.0b1 is released a few days ago and already shows positive results in performance, it runs faster, uses less memory and has nice new features! The most important improvement is the performance, Firefox was the slowest of the 3 especially when starting up and had a memory leak that let it consume lot of memory quite rapidly. I didn't care so much, when I browse I rather have full use of my system, so if it uses a lot of memory so what, but then again memory leaks are never a good thing.
Already many people wrote something about it on their blog, but there is only one that I read and find interesting enough to link here. And that is: http://blogs.zdnet.com/hardware/?p=960 an entry made by Adrian Kingsley-Hughes where he writes a little about memory usage.