See, the thing is, I consider GMG to be decent, but only because they offer Steam keys. So basically, they're Steam to me. Of the others, I consider only GOG to be good, and in fact they're the best because they offer DRM free downloads in such a way that even if they were to go down tomorrow, I would be able to access my purchases indefinitely.
There are a few more, but they are absolutely awful. Basically, I've only found Steam and GOG to be worth my time.
Amazon is pretty great, allowing you to download directly as well as giving steam keys for games that use them. Gamersgate, gamefly and GMG are good, but I only use them for steam keys typically because I don't trust them to stick around.
"Nerd" and "gamer" have become the ultimate consumerist identity. Completely devoid of values outside of consumption without reflection.
If this is true, it's disappointing how companies are handling digital distribution. I hadn't had a problem with Microsoft's service before, but being able to restrict access almost entirely to somebody who purchased your product sounds like a pretty jerk move and something to be wary about when deciding to go digital on a 360. I dislike that Nintendo doesn't have any account system and that losing or breaking your 3DS might cause you to lose your downloaded games. I haven't had a problem with Sony. I like where they're going with the digital downloads. They did something similar when they removed Fate/Unlimited Codes from the PSN, but they at least allowed people who bought it to redownload it.
I recongize the negatives of this type of service, but I also see the positives and like what it brings to the table (multiple games on handhelds and consoles, clears up on clutter, you can't lose a digital copy). It's too bad that not many get it right.
I'd like to point out that while Steam, another digital distribution service, does remove games from their market from time to time, you can always redownload and install it from your library. As far as it seems, Games on Demand seems to be the only DD service that doesn't let you redownload games it no longer sells.