Prevx

Prevx is going to get a free referral out of this story (don't say I never did anything for them! :-)).
I recently tried to help out a friend whose Useful Internet Speed had decelerated to approximately zero, even when she was using my DSL wireless connection. All of her available bytes, as it turned out, were being eaten by a worm who was furiously calling home about every millisecond or so (give or take 999 milliseconds). Her free antivirus program kept jailing a particular file (repeatedly, with accompanying pop-up notifications), while the real culprit continued the calls home, seemingly unhindered. Hey, at least her AV program could identify that a problem existed!
I took a peek inside the AV jail and googled the incarcerated filename--which is how I stumbled upon Prevx, who had the offender listed as 'bad'--known malware. Sophos also came up in my search, with a cure as well (which was most readily available by installing Sophos and going from there). Not seeing any $ signs around, we downloaded Prevx1, which munched and ate the worm and it troubled my friend no further. (She can now use her internet connections without help from homesick worms.)
Now here's the "catch" with Prevx--it's free! That is, its preventative powers may be used indefinitely at no cost. But if you want to use its curative powers (to munch worms, for example) you must pay. Now you can pay per incident, or you can subscribe. I suppose that theoretically, if Prevx's preventative powers were adequate to forestall any threat (and you had only one single problem to fix at the outset), there would only ever be one incident to pay for. Well, I chose to subscribe, and I'd bet most people do.
Prevx works on a somewhat different principle than your typical AV application. It's kind of like a citizen militia out to protect its citizens. It is advantageous (for Prevx's threat database, which relies on the "community") to have as many citizens as possible join the militia. Oh, wow, I can see it now--"The People's Prevx"! Oh my, I shouldn't have uttered that without asking for royalties :-). Anyway, Prevx works on this concept that 'more members' mean 'more information' and a more effective data base.
By way of conclusion, I do consider Prevx (be it free or not) worth checking out. There are some interesting stats compiled about various threats, and theoretically, it will protect us more rapidly than a paid Force--being comprised of a (hopefully) large number of citizens like you and I!
If you've tried Prevx (or its cousin Cyberhawk) please pitch in a tell us about your experience!