GOG.com announces a new money-back guarantee policy for games purchased through their digital marketplace with irretractable problems. This is now in effect, and also applies retroactively to games purchased within the past 30 days:

So, you bought a game on GOG.com and you've run into some trouble launching and playing it on your system, despite the fact it meets the specs we've put on the game's catalog page? This happens rarely, as our test lab does its best to assure your experience with our titles is as smooth as possible. But it does happen. And when it does, we want to give you the best support you'll ever get from an on-line store. Just navigate to our Support section--it's quite possible that the solution to your problem is already posted there. If not, just fill in a ticket describing your troubles and our top men will do their best to fix it all for you, so you can enjoy your purchase.

But what if they cannot find a solution? If such a rare event should occur, we'll give you your money back. Simple as that. If you buy a game on GOG.com and find that it doesn't work properly on your system, and our support cannot fix the problem, you get a full refund. It's a worldwide guarantee, and you have whole 30 days after the purchase date, to contact us about the refund.

There's even more! If you bought a game by mistake, or simply changed your mind about a purchase, you can get a full refund within 14 days, as long as the game wasn't downloaded. If in any doubt about our refund policies, please consult our FAQ.

We hope our Worldwide Money Back Guarantee will make you feel secure while you expand your DRM-free catalog on GOG.com. Having that said, we're confident that our titles won't give you any trouble in 99.9% cases!

NOTICE:
Even though this policy is introduced today, its effect goes back 30 days. If you bought a game within the last 30 days and have any of the trouble described here, contact us! We have you covered.