Ranked in these QuestionsQuestion Ranking
Pro DRM free as a rule
Good old games refuses digital rights management on principal, your binaries are your binaries and they work wherever they can work.
Pro Seasonal sales
gog features summer and winter sales every year and offer quite a lot of games at lower than retail prices.
Pro Money-back guarantee
If GOG can't help you fix a game, you're free to refund it within a month of purchase.
Pro Regional pricing
Pro Client is completely optional
You can either download games directly from the site or use their Steam-like client, GOG Galaxy.
Con Limited, often dated, library selection
Good old games focuses on resurrecting the wonderful games of a decade past, these are the titles publishers are most willing to give up drm control over and turn another set of profits on.
Few recent released are joining the platform at time of writing. Expectingt to see large publisher conglomerates like EA ever recognizing the gog platform over reselling their own drm copies of legacy games is not likely.
Con No Linux client (yet)
They say it's coming...and you can still install Linux compatible games directly.