One of the groups that I have at work is Managed Services that we provide virus and firewalling for over 10,000 networks nationwide, we get all kinds of opportunites to work with other applications like antivirus and spyware .
We sell a package called McAfee Small Business systems it used to be called McAfee ASAP. Its fast, very lightweight and does a great job. If you do not have a hardware firewall the package comes with a software one, virus detection, adware and spyware along with what they call Site Advisor which integrates with google. You can get it all for about 35.00 and it works good. AVG is good but with anything free there are limitations...
I personally have had more issues with Symantec then any other protection out there... I have over 30k machines on Altiris and its now owned by Symantec so not all products are bad.....
just my .02