Been using Avira since I updated to Windows 7 over AVG Free.

I swore by AVG for years, but it seems they have become massively bloated over the last year or so. And I just wasn't as thrilled with it anymore.

I did like Avast, but the updates were fucked with it. Half the time it would update, other half it just wouldn't.

So Avira gets my vote. Lightweight, fast, efficient, and safe to boot! No complaints from me, really.