Recs.
Updated
Specs
Pros
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 Money back regional pricing
GOG may charge more in some regions as publishers request so. But in those cases they give the extra cash back as credits for buying another game.
For example, the lowest price for the game is U$20 in US, but if in your region it costs U$30 they will give you U$10 back as credits for your next purchase.
Cons
Con Galaxy is mandatory
Even if they say it is an optional client - many features are only available by using the Galaxy-Client. It's also the only official way to download files from the GOG-Site with a download manager.
Con Still a proprietary service
GOG is still a proprietary service so it's not really better than Steam on this side.
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. Expecting to see large publisher conglomerates like EA ever recognizing the gog platform over reselling their own drm copies of legacy games is not likely.
Recommendations
Comments
Flagged Pros + Cons
Pro Galaxy is proprietary
Galaxy is built with many open-source tools but is itself closed source.
Pro Client is completely optional
You can either download games directly from the site or use their Steam-like client, GOG Galaxy.