Good post, some good points.
One more point - use a proper firewall (Sygate etc) and disable Windows shares completely. If you need to share something on the network, make the share readonly. If you have to share something read-write, then give the share a good, strong password.
Enable Windowsupdates (if you can). Sometimes Microsoft will release a patch which will prevent a certain piece of malware from infecting your PC.
I've put Avast on my wife's laptop, and she's happy with it. Previously it had AVG free, and she was complaining about the laptop being slow.
Recently I had some sort of worm at my company, infested a couple of PC's. I tried to clean the infested PC's, but nothing worked. In the end, a backup of the user data, and a full reinstall of Windows was the only way out. I upgraded Windows to SP3 while I was at it.
Looking back at the viruses/trojans/worms over the years, one can be amazed/horrified at how complex they've grown - the first virus I've got to known was the "Stoned" virus, with its "Your PC is now Stoned" message at boot up
