eumerius: I've just tried it and it is super awesome. Nothing negative about it. I do not understand why some people do not like it.
I am mostly indifferent about it, as long as I am not forced to use it for single-player games.
The plans to include it on all GOG offline installers sounds negative, mainly if it considerably increases the size of all installers for something I don't intend to use. If they leave only a small (2MB) stub installer there, I'm fine, but I still feel they are doing a rather odd move pushing Galaxy (since, people who decide to download offline installers are basically those who have decided not to use Galaxy, so why push it to them that way?).
Like someone said, if I was really into using a store specific client to manage and run my games... why then wouldn't I simply use Steam instead? What is the benefit of using Galaxy over Steam? For the few games that GOG has but Steam doesn't?
Yeah, to me that I can have client and DRM-free single-player games from GOG, is the reason to purchase from GOG. If not, then I guess Steam it is.
For instance, I already had e.g. Fallout 3, New Vegas and Oblivion on Steam, but I just repurchased them from GOG. Why? Because with the GOG versions I don't have to use a client and they are officially supported as client- and DRM-free. If the GOG versions would have required one to use Galaxy to play them... then why would I have bought them on GOG (instead of Steam)?
Question back to you: what are your reasons to buy a game from GOG, instead of Steam? Since you are fine with clients, why not just use Steam? Or do you buy from GOG only in those rare cases that some games appears on GOG, and not Steam, otherwise you buy everything in Steam?