I just used Nortons for years ( a decade or so). Then, about the time Darkfall came out I bought a new pc and it came with McAfee trial, so I have been using that for the last several years. I just really haven't had any issues to speak of. Twice, maybe 3 times since I started getting online in the early 90's have I gotten some malware on my pc that the AV didn't handle. And those times, I just did a quicj search (from another pc), found out how to fix the issue, and fixed it manually pretty quickly.
So, as far as I am concerned, what I have works well, I am happy with what I pay for the results I have. I can't recall ever having any issues with my AV affecting any software I was wanting to run or anything like that either.
As far as free AV software, well, I am am a firm believer in you get what you pay for. I am not silly enough of a person to go spend $100k on a vehicle when I can get a nice car for around $20k. I am more in the lines of the person that would buy a used car for around $3k to $5k but won't even think of buying a used car for under $1k (my future son-in-law is dead set on buying a car he found for $600. I tried to explain to him that it wasn't worth it. If it's that cheap, something HAS to be wrong with it.) And I know the free AV software is good, but I personally just can't get past the uneasy feeling it gives me. To me, it would be the same thing as someone wanting to give me a free alarm system for my house, or a security guard that wants to work for free. It just gives me an uneasy feeling. Im happy to be paying someone that does a good job, in my opinion, less than 15 cents a day to keep my PC safe.
But, I am a silly old fart, and set in my ways on some things. :D