I concur, running without anti-virus is foolish, no matter how safe you surf. The bad guys are always coming up with new ways to deliver virus payloads, and what you know to be a safe practice today may not be safe next week.

I've been running AVG for years now, since AVG 4, now at AVG 8.5. The early versions were CPU-intensive during scans, but that problem seems to have been solved. I have it set to not nag me and not pre-check the links, and it's done a great job for me at a price (free) that cannot be beat.