Be sure to grab the latest version of Firefox from Mozilla on June 17. This is the fastest and trimmest version yet.
Speed tests are showing a 2-4x improvement over Firefox 2 and 9x over Internet Explorer 7. Memory usage tests measure that Firefox 3 is 2x more efficient than Firefox 2 and 4.7x more efficient than IE7. There’s been a tremendous focus on performance for this release, and an incredible amount of effort has gone in to achieving these numbers.