I work for a non-profit and we use the free version of AVG at the office. I should point out that this really shouldn't be taken as a solid endorsement, we're very security conscious, just not very tech savvy.
At home, I have My Own Personal Geek (he is a computer programmer), and he has installed ESET Node32. No clue what that means, but he took Norton off. Norton used to be the best (Symantic) but now it is more of a pain the the tushy than anything. (how can spell-check not recognize tushy??)
Anywho, I don't have any advice on whether to pay for AVG or not, but I have been told the free version is actually pretty good. At work we don't need the anti-spam from the pay-version because we use Postini, and we have a firewall built into the server, so the free version is fine for us.
At home we have a magic unicorn protecting our network with faerie dust. *hangs head in shame* I know, I really should know what we have at home, but my head starts to implode when my geek gets his geek on...