I'm running Trend Micro paid version on two Win 7 64-bit PCs. Seems OK so far but only installed one month ago.

AVG free on one PC, seems OK too.

AVG Business Edition on 10 PCs, OK too but don't really know what extra you get for the paid version compared to Free. I have used Customer Support on a couple of occaions and they responded in less than 2 hours (business hours) so I thought that was pretty slick

My business laptop has Symantec Endpoint Protection as that is supplied by work. I never see it pop up any warning messages. To be frank, I don't even know if it does anything eg. I have never seen it run a scan of my computer or say its checking an email or a new application. If its "on" then its very quiet.

Some other systems on Linux Gentoo 64 and my Sys Admin (my son) says "pfft ya don't need antivirus shite sucking resources from your crunchers."