After having some performance problems with Firefox 1.07 (slow-scrolling text with the new design on Joel On Software), I opened Firefox 1.5 Beta and tried viewing the page with it. I found that not only was the scrolling issue gone in the beta, but that the time it takes to go back to a previous page is much quicker.
This is good to see. Firefox is playing a key role in moving from desktop applications to web applications. They have long been good about implementing new features, but with the current generation of web applications, a lot of work needs to be done on other things, like performance.
I see a lot of exciting times ahead for Firefox.