I'm an Outpost Security Suite user, and I've used various anti-malware solutions over the years - and still sometimes do (for example, the machine at work has some variant of McAfee on it because I have nothing to do with the management of the machine).
In my experience, all anti-malware causes me pain. Mainly because when they report a problem there's so little useful information about the possible threat that I can't really make a good determination about whether or not it's a false positive or a real problem, And I suspect that most of the popups I get about possible malicious network traffic are in fact false positives. But I usually go ahead and choose to block whatever the anti-malware is complaining about and rarely run into problems because of it.
Anyway, I used to sometimes use free solutions, but have mostly moved away because I found that they tended to require more manual maintenance. Often one of the features that a free solution doesn't have is automatic updates. I like my anti-malware to be as maintenance free as possible, because even the least in-your-face of these products seems to periodically want to ask you a bunch of questions that you can't reasonably answer anyway.
So I got a 3 PC Outlook Security Suite lifetime license way back when, and as far as I can tell it's served me as well as any other anti-malware has (or would have).
Basically, I see this class of software as a necessary evil. Every now and again I teeter toward considering it unnecessary because it sometimes seems that anti-malware causes at least as many problems as malware itself would. However, I'm rather afraid of some of the malware out there, so I put up with the anti-malware because I don't feel that I understand how to effectively deal with it myself, and I don't want to take the time to become an expert. I sure don't want to get hit with a crypto-ransomware trojan, and I hope whatever anti-malware I have will protect me from that. Currently I run Outpost Security Suite and Malwarebytes at home.
I know it's kind of a lukewarm endorsement, but I think that's more about the anti-malware software market as a whole rather than Outpost itself. I'm happy with my lifetime license purchase - I don't think I'd be any better off with another solution, free or not. Since I've already paid for it several years ago, and the cost wasn't really anymore than a single year 3-PC license would have been, it's essentially free for me from here on out.