Safari is faster, and is a better user experience for me. The main benefit is the native iPhone sync. I use FF only when a site is coded poorly.
I do have a few FF extensions installed, since I use it every time I’m working on a site design. I use Firebug, Google Gears and RSS and Page Validator. I was using Video Ook! until the upgrade broke it. Now I have to go back to outboard tools to yank video from the interpipes. I have Universal Uploader installed, but I don’t know that I’ve ever used it. I’ve got a few others installed mostly tools for designing/coding sites, even one to replace Ook, but I’ve never used it. You should check out GSpace if you haven’t already, lets you use your Gmail account as an online storage drive. I have .Mac so I don’t use it, but it’s cool anyway.
I always say I’m going to switch to FF all of the time, but I just don’t… probably mostly due to iPhone junk. But I definitely really like the browser. I think anyone not using it on Windows doesn’t like themselves very much.