I've been a FireFox fan since version 1.0.Now, with the fierce browser war between FireFox, Safari and Opera, they are just getting better and better.
Get FireFox 3, it has better performance (for newer software system requirement, this is often impossible), better browsing experience and lower memory usage than its previous version.
I've been a test user of FireFox 3 since last year - it really is a worthy upgrade over version 1.0, 1.5 and 2.0
Take my word on it - FireFox 3 is great.
(To download, just click on the FireFox banners above)