I have AVGAS, A-Squared, SpybotSD and Ad-AwareSE and I regularly update each (daily when I manage to have the time to go online) and do a quadruple-redundant scanning every other day. I'd say AVGAS (yes, it is the former "widow") is fine and at par with A-Squared but I always feel compelled to have Ad-AwareSE to take a third look after the two, reboot and go to safe mode then have SpybotSD make a final check.

I have no complaints but I do feel a little more confident having those four around since I've observed that some signatures are invariably found by another where a former hasn't.

Still... there's the anti-virus and the firewall at work, yet I don't really feel THAT secure (unless I stay offline for a time and with no other disk or cd inserted into the drives). Perhaps rightly so, IMHO.