I've been using Avira for a year now, do heavy torrenting, never have my firewall up, am totally opening myself up to idiots hacking me now that I say this ... but have yet to have any issues with it at all.
I usually use AVG, but decided to try Avira out on a recommendation from a techie friend and I have to say that for me, I like AVG better, but Avira does a bang up job.