To me, this is simply the single most important retail service in PC gaming history. I honestly mean that.
Some developers/publishers have removed the DRM from particular games after release, and some release games with no DRM at all, and I am thankful for such things, but in the world of commercial game development these are mostly scattered events.
To create a business based around the idea of re-releasing classic games from multiple origins (and in increasing numbers, we can only hope) free from the DRM that once encumbered them (not to mention compatible with modern PCs, and at such good prices)... that is something entirely different, and something that I honestly never imagined would happen.
I feel as if there may only be one shot at making this idea work, so I fervently hope that the feelings I see here will prove representative of the gaming public at large, and that GOG will be the success that it desperately deserves to be, because the long-term benefits will be absolutely huge.
Thank you GOG, and good luck. May you get the support you need from gamers, publishers, and developers all.