My 2c

AVG has seriously gone down hill the last couple+ years. I've used free & paid versions. I no longer run (free or full) AVG on any machine.

I do however run the stand alone AVG LinkScanner on a few machines. It is 'OK' but can cause brief hangs in the browser here & there. The whole AVG toolbar situation (upon install & after) is obnoxious at best.

As far as Avast is concerned.. I've tried to choke it down a few times but just never end up committing. Last time i checked it ran more like nagware and required signup/subscription/blah blah not even sure the free version is ultimately free &/or doesn't expire.

MSE just kind of fills a gap of *something* being there that doesn't seem to cause complications or require frequent attention.

On a few machines (depends on type of user(s)) i run:

1. AdblockPlus
2. NoScript (for more experienced users)
3. AVG Linkscanner
4. MSE
5. Statically Assigned Norton DNS servers (nortondns.com)

No one hates Symantec & Norton products more than i do but the free DNS service they provide surprisingly seems decent. Obviously a router can be set to their dns servers too covering the machines on a lan easily.

Those items combined (in combo of firefox obviously) seems to be about as effective as it's going to get for an end user.