I'm not saying paid AV's aren't worth it, but, as I said, I've never had a serious infection or problems with a free one.
You can find reviews for most, if not all, AV's/Firewalls/etc on the web somewhere. Read up on them and if you like what you hear give it a try. You can always switch to another.
In terms of reviews, find ones written by actual users. You can never be totally sure "official" reviews haven't been influenced by "incentives" for a good review.
People cannot complain about getting viruses if they're using the free versions of any of the Anti-Virus products. Purchase the products. Free technical support & full protection. AVG Internet Security works very well these days and I find it doesn't slow my PC down like Kaspersky or McAfee! Another good product is PrevX. It's new and can won't replace your current anti-virus. It finds all bad files on your PC! check it out: www.prevx.com/
I know that AVG has some problems but i think it's a trustworthy antivirus. Personally I use Eset security.
Just because you pay for something, does not automatically make it good.