I like the sound of this. Steam has really dropped the ball on its quality control as of late, so I'm very happy to see a company like GOG with their usually excellent attitude towards this sort of thing (along with DLC practices, etc.) providing this service.
I buy my games on GOG where possible anyway because I like their DRM-free games and their fair price guarantee usually means the games are cheaper. Their sales have even been cheaper recently with Steam not running daily/flash sales any longer... I'm not hating on Steam or anything, but I think far too many people foolishly refuse to use anything but Steam believing Valve to be incapable of wrongdoing when quite the opposite is true.
I'm all for the competition. It might force Valve to get their act together and start curating what they allow onto their service!
As below, I don't buy into early access either with the exception of superb examples that are worthwhile in their current state and continue to be updated. I think games like Kerbal Space Program, Prison Architect, and the recently released Darkest Dungeon absolutely deserve the support throughout their development. It's just a shame some studios take the ****. Looking at you, DayZ...