On the subject of antivirus programs in general:
I've been holding back installing anything, given the firewall which came with my system (OS X 10.7) and the fact that very few bad things seem to infect/affect the Mac.
And given the discussion herein, I've restrained myself from installing Sophos 7.0.5 (which I have lurking in the shadows).
What, if anything, is the experience with MacKeeper (new to me)? I'm not impressed by the reviews.
Edit: This post was a originally a reply to Re: sophos antivirus and has been moved to its own thread.