Firefox 3 > *
So the IT security software on my computer at work said I had to upgrade to Firefox 3.0.1 or die. So I upgraded thinking, "It's out of beta and people have said good things so what the hell?" Firefox 3 is amazing and my current browser of choice.
Some things I like about the new Firefox:
- Faster rendering of pages
The pages render much faster in Firefox than in IE 7. However, I have read that this is due to certain hacks that Firefox uses. I have read that it downloads images, text, and other things that really matter to humans reading it. Safari is faster on the rendering side, but it has much more bloat. (Gadget Zone) - Tab Responsiveness
The tabs respond much faster upon creation. Not to mention just normal cycling through is much quicker than IE 7, but that's always been the case. 
Subtle UI Improvements
There are a few nice little UI improvements. The star in the address bar to store bookmarks is really cool. When you click the star it adds it to the "Unsorted Bookmarks" folder. My gripe with it is that it not easy to access the "Unsorted Bookmarks".
I'm waiting for Firebug to get out of beta for Firefox 3, but aside from that all of my other plugins had Firefox 3 versions.
I'm going to continue using it for a while and see if any issues arise, but I realy like it.