Used to use firefox, but recently switched to Safari. Maybe when firefox 1.5 is released i'll switch back, but I like safari so much more now than firefox. Looks better too. I really hate the way skins work with firefox on a mac.
I have been running tests with Camino, Opera, Firefox and Safari. I mainly use Safari, but recently because of sluggish activity I have been using Camino. Camino works quite well and it handles quite a few sites the cause Safari to crawl. Opera however as mentioned earlier is probably the oddest looking browser out of all of them. I am not too fond of its looks, however its performance is pretty good and worth a second look.