I'd never run without an AV, not that I visit any fishy sites or anything, plus all my software are legit and paid for. Just to have that extra sense of security.
Since I am crazy about performance, I have tried all AVs, and have a license for the most popular ones......after trying them all, I chose to use the new Norton Security as it has the least footprint with no noticeable loss in performance and no false positives, it never bothers me or comes in my way. Plus their new licensing system rocks! you pay only once, and you can use it on up to 5 devices, no more buying a separate license for every device you own.