I actually stopped running resident AV programs on my main machine (still scan every couple weeks with a couple online spots) and have never had a virus detected (even in the 10+ years before I stopped using AV). Just use FireFox with NoScript and exercise a little common sense and you'll be alright.
Don't get me wrong, both laptops, and my other 4 desktops are A/V protected, but my personal machine is not. Yes, I am prepared at any time to nuke this entire system if need be.
Oh, I use Avast! on my Vista and W7 machines, AVG on my XP machines. They just seem to work better that way.