Any Linux distribution is a good anti-virus, I agree. Also, if you have a router, it is probably a hardware firewall. I haven't used anti-virus for a couple of years now, nor a software firewall. I just don't need it.
That said, if you like finding "free" games or pron online, you're flying on your own.
Posting on a Linux box, with Clamav running.
Though reading about Windows 7 with the Virtual XP today on FR, I must confess that actually sounds intriguing.