The haters will tell you that because AVG doesn't detect more than about 85% of all currently known viruses that it sucks or whatever. If you aren't surfing websites of questionable repute or transporting floppies or other removable media in and out of it all the time and if you're behind a hardware firewall like most current dsl/cable routers, that's a moot point. Most people get nailed with the popular stuff, like the Storm worm. AVG is very good about updating to protect against those. The other stuff is so rarely seen outside of college/school computer labs that for most users it doesn't even bear mentioning.

AVG is also VERY friendly to your system resources while still providing real-time file system protection.

/shrug

[edit] With the other stuff you're doing (firefox + adblock + noscript = HUGE) then you're pretty golden. I've been using your plan + cable modem router + AVG now for about 3 years and I've had zero infections on 5 PCs.

P.S. Yes, I use "haters" because the topic of anti-virus solutions lately on generalist forums has become less based on realistic facts and more on ballpark absolutes and fashionability.