MorningStar33: Las time I checked, it was awful. You couldn't configure practically any settings.
MaximumBunny: You can set exceptions. In Avast you can...adjust the voice? Adjust the animations? Change the theme? Because that's what really matters.
I'm not talking about aesthetic settings, I'm talking about technical aspects. And yes, Avast has a shitload of configurable options of that kind.
pretumos: I was also getting problems with Avast causing havoc on GOG Galaxy. When Galaxy was doing its own self-update, it made it fail every time. Also, when trying to download game updates, it was either shutting Galaxy down, or making the download stop (and you got this error: "INSTALLATION FAILED: DISK ACCESS PROBLEM").
Disabling all Avast shields (while the downloads happened) let me bypass these problems.
This is a known issue with Avast and at least 1 other AV - Comodo.
I've reported it here:
http://mantis.gog.com/view.php?id=1984