nmb11999: Even though I got my steam key already, I think I'll just stick around here. I quite like the idea that you can run the game without have to start up a client, and that you can also decide yourself when you want to download updates, etc. Those are really nice features, particularly with something that's still in development.
The big reason I stick around is that GOG actually allows me to own my games. I can take the install files, stick them on a external and they are there when I want them. No worrying if my internet goes down, no worrying if my Steam account gets locked, no worrying if the Steam service is down, even if GOG goes out of business tomorrow I still have my games. I can't say the same about Steam. With Steam I feel like I rent the games and can use them until Valve says otherwise.