I run Avast! too.

When I first installed and did the full scan it reported several viruses that weren't really viruses, as best I could tell. All complaints it made were related to some long-named Sysinf.......... series of files.
When I enquired to Avast! they said that the files were related to system recovery checkpoints. I turned off recovery and turned it back on, just to get rid of those files.

Anyway, I honestly don't know how to 'measure' the effectiveness/efficiency of AV software. I suspect that some of them could periodically report false things just to make themselves look valuable.
I certainly feel that is the case with Postini. I pay my ISP extra to run that, but I'd bet that it lists extra SPAM just to make it look good.

Good luck. Overall I can say I'm satisfied with Avast!, but I do use the 'pro' version.

cheers

>Looking for suggestions...
>
>What antivirus are you using? Are you satisfied?
>
>I've used Symantec in the past, but it use too much resources IMHO. I currently use Avast, but I have some doubt about it's efficiency. I ran a complete scan this weekend and it found 5 virus in my system. My question is: why did they get in in the first place? Isn't it the job of the antivirus of stopping the infection before they get in the system?
>
>TIA