I'll second that. Only annoying thing is the popup once a day that wants you to  purchase the paid version. The free one is fine and with just one click the  popup is gone.

Another good one that I'm also using is PC Tools Firewall plus and Threatfire together. Nothing to do there either.

Both are free and I haven't got a virus yet. Of course I use Firefox and online E-mail accounts which greatly reduces the risk.