For me personally, I'm hoping the Bloodrayne games end up being a part of it. I own them on Steam but the Steam versions have problems, like Bloodrayne 1 has issues with dialogue syncing in cutscenes where characters get cut off, with the apparent reason being that high framerates actually screw with cutscenes. Bloodrayne 2 has it the worst though as cutscenes have severe issues in the Steam version, usually with the picture blacking out and you can only hear sound. From what I've heard, the GOG versions have fixed these issues. I think Betrayal is comparable on Steam and GOG though, but hey it'd still be nice to have a DRM free version from GOG anyway.

While I DO already own this game on GOG and Steam (got it on Steam first a couple years back, and I got the GOG version as part of that Interplay sale bundle a while ago), MDK really needs to be a part of the program simply because the GOG version actually includes the 3DFX version of the game, which is the only one that works properly on modern operating systems, while Steam only gives people the DirectX version, which does not work properly as it results in missing graphics. As such anyone who owns the Steam version and feels like they got "screwed over" because maybe they bought the game before Steam introduced refunds, now they'll actually have a properly functioning version of the game.

Lastly I'll include Slave Zero. Why? Honestly, this one I'm only putting here because I originally was gonna get it on GOG at first but ended up getting it on Steam because I think it was part of some bundle deal, though heck if I remember which one.

I regret having bought The Witcher 3 (together with the season pass) from steam; if I could get the gog license either through the 'backup' option (already available for TW1 and 2), or through connect, I'd be really glad.

Not to mention, games like:
TIS-100
Super Hexagon
Olli Olli 1 & 2
Not a Hero
Mark of the Ninja
Metro 2033 & Last Light
Dropsy
Assassin's Creed

OT, that is the most adorable avatar I have ever seen.

Eh... I can't think of any. I already own most of my steam games available here. Maybe Divinity Original Sin. Not the enhanced version, since I own the regular version on Steam and have both there but only the enhanced one here (I bought too late here)

Well, the plan was to rebuild steam library at gog as much as possible. Already have some duplicates here and there and I don't really mind to be honest.. What I want is more classic games and perhaps some newer ones released on gog : )

Skyrim.

Morrowind :-)

Homeworld Remastered.

I'm not really interested in duplicating licences I already have, but I wouldn't mind a copy of STALKER: Shadow Of Chernobyl here because I can't get my Steam copy to work, and it's a game I'd really like to try.

Batman games. Fear 3. Namco Bandai's cr@ppy ports. All in all, those are 10 titles and the only games i own on Steam. Can't wait for them to show up in GOG. Can't wait to get rid of steam permanently.

Darksiders 1&2
Transistor
Couldn't you get a CD key for that game and reclaim it on GOG even before GOG Connect was introduced? Or did your Steam version not come with a key?

It's not duplicating licenses, your not getting a second license, its simple the publishers honouring the license you've paid them for with a DRM Free GoG version.

I did try that, but the code showed as invalid. I never bothered to contact GOG support but you've inspired me to do it and I've just sent them a message. Fingers crossed!

try here