Wow, lots of arrogant-sounding advice here. Lots of "unless you're an idiot, you don't need AV protection" sentiments as well (and don't tell me I'm off-base with that interpretation; words very much like that were used in one particular post).
While some of the people who brag about never using AV protection say they have had "only one or two viruses for as long as I've used computers", I have never, EVER had a virus, worm, trojan, or other malware activate on my system. I have downloaded perhaps two or three of them over the years, but I've never activated one--whether or not it would have done harm. This isn't because I haven't been around long enough, or because I don't download software.
Saying "shucks, I got a virus once, but it didn't do any harm" is missing the point. Saying "gee whiz, I can reformat" is just as bad. The reason is simple... what if your next malware isn't a virus, but a remote-access trojan (RAT)? What then? You'll do your proud reformat after some 14-year-old scumbag has scoured your entire system?
I run PC-cillin 2003, and I detect no performance loss whatsoever. Maybe I could detect a minor slowdown if I tested with two identical systems side-by-side, the only difference being the presence or lack of PC-cillin. Maybe. But even then, the minor slowdown would only apply to application launch. Show me the benchmarks that prove otherwise.
I do understand the frustration, and the ill will. I've suffered with crap AV software. I suffered crash after crash with Panda, weird system behavior and lack of reliability with Norton, nonexistent trojan detection with EZ Antivirus, and so on. But I didn't give up entirely.
You guys who advise against running AV protection are being irresponsible, as far as I'm concerned. You should run AV (and sometimes also AT) software on any system that ever has new software installed on it--no matter how safe you think the source of that software is. The reason isn't because "well, I'm a moron; I better use AV protection!", but rather because any responsible security approach involves layers. And "gee whiz, Mah, I think that shareware site is legitimate" does NOT cut it.