I’ve used avast (free version) for about 4 years now. I’ve been happy with its protection and frequent virus data base updates (about 2 per day on average). I’ve not gotten a virus/malware infection on my PC in those 4 years.
Consumer Reports (June 2011 edition) just reviewed security software — both free and paid versions. Avast is listed as 3rd under the free versions just behind Avira and i[/i] AVG… but ahead of Microsoft’s Security Essentials. Just as additional info, Kaspersky was rated at 6th in the paid versions (McAfee – which I used to use – near the bottom at 13th.).
I could scan a copy of their chart but that would be copyright violation. If interested this issue should already be on magazine stands.