I left firefox 2 for almost a year now. I only use firefox if I need to debug html or css from website using web developer add-on, which I rarely do lately. Firefox 2 is slow, eats my memory, and doesn’t blend with my others gnome applications. Firefox 3 bring the design to the new level. It implements gnome icon theme, and better design integration.
I might turn back to firefox 3, since the power of add-ons in firefox is so tempting, and bring browsing to the next level. I have to try that.