qwixter: It's a bit like would you develop a game for Windows or Mac/Linux first? While everyone thinks it should be all of the above, it's really not free and it takes longer, then there are the support and testing costs and time for additional platforms.
I think nowadays, you have multi-platform libraries for games that take care of things like graphics.
Those library might not be suitable (in terms of optimization) for the most demanding AAA, but they would certainly do the trick for the majority of Indie games.
For me, at this point in time, an Indie game is that Windows only indicates that the dev didn't pick the right technologies for the job. Why you would deliberately lock yourself in one platform is beyond me.
qwixter: Then if you do decide to use gog, and have multiplayer component, be prepared to write your own matchmaking service, otherwise put up with the complaints of gog users. If you try and use gog galaxy client for it, you hear drm complaints. If you have a windows only game, you hear the linux bunch complain. As a dev, I wouldn't even put a screenshot on this site.
Yeah, I think we are in bad need of an open-source match-making service for games with companies behind it for the back-end part.
KiNgBrAdLeY7: In the end, we gamers treat GOG like shit. We can't be patient and wait, we have to rush in to buy the new and shiny, we end up doing some of the things we accuse and we don't display our "disagreement" with vile policies as strongly as we should! Keep in mind that inaction is co-guilt, too. Don't nag when we get fucked, you supported our fuckers either directly, or indirectly, through 1 or more means!
Personally, I only buy DRM-free (mostly on GOG, a few select games on DotEmu and Humble Store).
Honestly, if there was a Netflix-like service for games (with similar rates), I'd consider using it and would still use GOG as a supplement to get games I really want to replay, but Steam is not that. Steam is more like "yeah, you pay a sometime large lump sum for individual game, but you don't really own them, you know... it's really a service disguised as a product".