Hi quickslvr,
I have no experience with the paid version; however, I do have a great deal of experience with their free versions, and I can tell you that the free version provides adequate protection for most individuals. I have been using the free version since Avast 4 (or maybe even earlier) and I have never been infected. The beauty of Avast is you get the warnings "before" a website can infect your PC (it blocks the download and warns you to leave the website). Right now, I'm running on the newly released Avast 8.0.1482 and it is running without issue on both of my rigs. Now, if you are interested in their paid versions, I would strongly suggest you visit their forums and browse for problems because I really don't think they have worked all of the kinks out of them yet.