My mileage is slim, since I don't use any AV anymore. In Leopard times, when I was quite new to the Mac platform, I used ClamXav (the ClamAV engine known from Linux, with some rudimentary UI), but mostly as an on-demand scanner. I set on-access scanning only to the default download folder, since this is the place where untrusted stuff from the 'net usually lands (or so I thought).

Since then, I don't use any anymore. I think AV scanners are snake oil, most of the time, generating a false sense of security and encouraging a more careless behavior, because of thinking "I'm save from harm, the AV's got by back". No, it hasn't.

It won't save you from yourself and your reckless behavior, because it can't. It won't save you from zero day exploits in the OS, applications, and browsers, because it can't. It won't save you from malware with yet unknown signatures, because it can't (heuristical scanners are even bigger snake oil). All it does and ever will do is looking for known attack vectors, which have become, by definition, obsolete by being known. Luckily, since most of the AV products are still free on the Mac (why's that so, btw?), at least there's no financial harm being done from using them, right?

Well, in the end they might cause more trouble than they save you from, but YMMV. Software incompatibilities, performance hits, false positives, these things have to be taken into consideration, too. Worst thing that could happen with a system-wide on-access scanner is that the update patch to the game goes awry and you have to reinstall from scratch. Or that the client crashes or disconnects due to desyncing, because it can't load it's assets fast enough into memory. Yes, you could make exceptions for game files and folders, but then you'll have blind spots on your disk. How good can overall "security" be, if it's compromised from the get-go?

Best line of defense is still practicing common sense, caution, and taking care. And making informed decisions. An AV scanner can't do that for you.

@Moonraker and @KhajitFurTrader‌: Common sense and a hardware firewall are a great foundation for Mac Security.

I find it helpful to know that the Mac client issues we are seeing exist for folks with no antivirus running.

I also suspect until the known issues with the ESO Mac Client are resolved, it will be difficult to fine tune antivirus settings with any degree of confidence.

I have aging parents who can and will click on anything or forward me files "to check". So I routinely run an antivirus to check those files. I figure a blind spot in a game folder is no worse than not running any antivirus.

In the past I have run without any antivirus installed. I do run a hardware firewall.

I agree about the "hassles" of running antivirus and other security software and have run into some really invasive products that do not "play nicely with the other children" and are very difficult to uninstall. Also many of the free products may have the hidden price of data tracking as those sites gather information with their software.