I haven’t come across anything truly groundbreaking in Firefox 3, possibly because I’ve become accustomed to much of the feature set through the Betas and RCs, but there are one or two improvements that are quite useful (as well as a couple of regressions unfortunately).
First the bad. When you view Page Info from the context menu it doesn’t give a link to the CSS file in the Media tab any more. I was sure it was there in 2 and a quick google confirmed this. This really sucks – I can’t see why they’ve taken it out.
Secondly, when I was looking through the options to try and return the aforementioned CSS links, I discovered Firefox had decided it was going to automatically download any future updates when they were discovered (I promptly switched the option to “Ask me…”). Bad Firefox.
Magic Address Bar
The good is good though. It doesn’t seem like it at first, but to my mind the biggest improvement of all is the address bar. Sure they’ve added a “Most Visited” folder to your bookmarks toolbar which (shockingly, given the title) contains a list of the sites you visit most frequently, but the address bar has some great, if not immediately obvious, usability improvements.