timppu: I use Firefox almost exclusively, but today I got a new update for it, and I have been unable to connect to gog.com with it. Odd. So now I am using Opera instead, at least I am now able to access GOG with it, albeit sometimes it gets slow or stuck too, maybe GOG is just overloaded. But Firefox hasn't been working AT ALL for gog.com today.

As for your question, what kind of browsing habits do you have, what kind of sites you visit etc.? E.g. mostly porn and gog, sometimes mixed together? I wouldn't use e.g. Chrome for visiting porn sites because I am sure Google tracks all that to you and then later sends assplug advertisements etc. to you all the time, thinking you are some kind of sex addict..

ShadowOwl: Hmm, Adblock Ultimate is being developed by Secure Download Ltd., which appears to be a Bulgarian IT company According to their (currently dead) website their services are or were covering this: ShadowOwl: The addon is apparently open source and free software (licensed under GPLv3) but I wouldn't trust companies which are working for those guys whose ads you're trying to block.

Anway, I highly recommend uBlock Origin, which is available for pretty much any widely used browser: https://github.com/gorhill/uBlock
It's also open source and free software, changes to the code are well documented via GitHub.