Just released is the all new, all sexy, Firefox 3.5.

New features include:

Performance.

Firefox 3.5 includes the powerful new TraceMonkey JavaScript engine, which delivers unprecedented performance with today’s complex Web applications.

Open Video and Audio.

Firefox 3.5 delivers the first native integration of audio and video directly into the browser. Now everyone can easily watch open format Ogg Theora videos.

Privacy Controls.

Firefox 3.5 includes features designed to protect your privacy online and provide greater control over your personal data.

Location Aware Browsing.

Location Aware Browsing saves you time by allowing websites to ask you where you are located.

Source

So far in my tests its a huge improvement on the last iteration (3.0.11) much speedier and handles the web better. I am really impressed with the native video player based on the HTML 5 specifications.