Tallima: It's pro-customer. And it's probably the #1-#3 reason GOG's customers shop here (I'd imagine price, reliability and DRM-free are top reasons).
F4LL0UT: It's odd that you don't mention the retro catalogue and GOG making sure that these old games work on current systems.
Only a few hours of sleep. I spent the night playing Civilization with my brother. My apologies.
#1-#4 reasons: those mentioned above! :)
I make sure game purchases that I plan to play in 5-10 years are GOG titles. I know that GOG cares about compatibility, and I know DRM won't hinder me from playing my games.
DRM can be almost invisible (my daily life, Steam DRM has only annoyed me a few times and prevented me from playing a few times). Or it can be a nightmare. I had an Ubisoft flight sim that had a decent manual (maybe 8-12 pages, my memory is fuzzy [as is everything after that play-a-thon last night]) and the manual was only about how to "play" the DRM. How to get online and deactivate keys before making hardware changes to your system. And how even if you did deactivate the keys, each hardware change had a point system. And if you changed enough hardware to earn enough points, you would win the DRM game (which meant you would LOSE the $30 game I bought). I was so disheartened that I quit playing it after a few days. I'm always messing with my hardware -- especially in those days b/c I had a budget PC and was always getting whatever parts I could get for free from hand-me-downs. I just didn't want to mess with it, even though it was supposed to be an amazing simulator.
I didn't buy Ubi games for a long while after that. I think Might and Magic X may have been the turn-around, I can't remember. But Ubisoft just makes some interesting, unique games and they make them well. So I get and play them now. Their DRM feels less obtrusive now. But I'd love to play Driver in 15 or 30 years and I'm not sure that Ubi will still be around then. So when UPlay disappears, so do my games. That sucks.
I applaud Ubi for putting what games they "can" here. But unfortunately, "their policy" is preventing them from DRM-free new games. Their spokeswoman was hilarious when she said it. As if they really wanted to provide DRM-free games, but this evil "policy" was just unavoidable. Drats! What 'evs. I try to buy their games on consoles b/c at least then I have the expectation of the game disappearing after a decade or two.