Firefox 4.0 Beta
I just installed Firefox 4.0 Beta. After using Google Chrome almost exclusively for the last few months, Firefox 3 feels very sluggish in comparison. However, when I open Firefox 4, the speed is increase is quite noticeable. For example, the new Twitter layout ran terribly on my PC using Firefox 3, but it ran excellently with Chrome. Firefox 4 runs it almost as well as Chrome, althought I did notice that it is missing some of the effects (the slide-out effect when you click on a tweet, for example) that are seen in Chrome. Still, I am impressed. The interface is more compact too, and better organized. They seem to have taken the hint from Chrome and abandoned the legacy menu layout that they were carrying over since Netscape Navigator. We'll see how it performs in day-to-day duties, though.
I am a little bored with Chrome now, since performance on YouTube seems spotty when dealing with their Flash-based ad overlay, and I'm seeing a number of pop-under ads when I visit less reputable web sites that are not present in Firefox. Maybe this is a problem with the Chrome port of Adblock, but the much more robust plugin support of Firefox is something that I miss.