My initial thoughts upon seeing the headline were that GOG was going to turn their storefront into a dumping ground for half-finished student projects like Steam has done over the last couple years, but it looks like they're possibly being more selective about the process, at least for now. Greenlight and Early Access could have worked a lot better if Steam restricted it to games that were already in a mostly completed state, and that they themselves thought were good, rather than anything that a developer can get pushed through Greenlight by giving away free keys and promising trading cards.
Witcher 3 Steam users got their saved games borked when patch came out.
GoG users, except for the early adopters, were able to avoid that bad patch and wait the 2-3 days it took to get a patch to the patch.
You can't really blame Steam for an inadequately-tested patch from the Witcher developers though, especially when those developers have close ties with GOG. One might even argue that they did that on purpose to make their own platform look good.
As in the last storm when we lost internet service, GoG users can still play w/o internet connection.
So can Steam users. If your Internet connection is out, Steam will start in offline mode. Running Steam in offline mode can also allow you to limit when updates are performed. And Steam's integrated DRM is actually quite mild compared to much of the stuff that was commonly in use before Steam became the standard, where third-party DRM could mess with system drivers and cause actual problems. Of course, some game publishers might still choose to integrate their own DRM in addition to what Steam offers, but I'm sure those publishers won't be selling the games DRM-free on GOG either.
Steam may have its issues, but so do all the other digital distribution services. There are things I wouldn't mind seeing them improve, but overall the system works reasonably well.