If so, are they full downloads to your computer where you install and play, or do they require some type of program that accesses the games like Steam?
I’ve bought about twenty or so games from GoG. You download the entire game and store it on your computer. You don’t need any sort of internet connection to play the game once it’s installed. GoG does keep a library of games you’ve purchased to redownload at your leisure, but you don’t play them directly from the site.
For some (very old) games, you may need to utilize some sort of MS-DOS emulator like DOSBox for the games to run properly.
GoG does that for you. The installer you download is a custom deal that (if necessary) sets up a DOSBox environment that launches automatically every time you run the game. Very little additional setup is required by the user - occasionally, you might have to set something to run in compatability mode, but usually the games run fine without any tweaking from the user at all.
This is my experience. I have Master of Orion I and II from GoG and they run in DOSBox on my Windows 7 system.
Awesome! I’m gonna get me some Master of Orion, Lands of Lore, Space Quest, and Alone in the Dark!
Worth noting is that the games have no DRM at all, which is really nice for those of us who don’t want to mess about with license keys and the like. And no, I’m not talking about pirating the games - at the prices GOG sets, there’s no reason not to pay for the games. 
I have a few and have never had any problems.
Yeah, i love GoG. I’ve been on a masters of magic kick the past month or so. I love Steam too, but mostly for the incredible sales rather than the service. They provide two different things really, GoG is more about classic gaming and Steam is (at least for me) very cheap access to current games.
I had some problems playing Kings Quest 7, but other than that they’re all excellent.
A few days ago I read something that reminded me of the old game “Theme Hospital”. Found it on some places around the net but couldn’t manage to get it working. Bought the GoG version and it works fine, no problems at all. I run Windows XP and decided to try setting the Windows 98 compatibility mode – bad idea – the game slowed way down and got all clunky. Seems like GoG does a good job getting old games in shape to run on modern systems.
BTW, Theme Hospital is a really good old game – very much worth playing unless you only like shooters.
I’ve reported the spam in post #10.
I have gotten lots of game from GoG - Castles II, Master of Orion II, Age of Wonders II (hmm why am I only getting sequels from GoG?)
They all run via DosBox, and works most of the time.
I bought Planescape: Torment from them. It downloads the whole game to your computer and it’s been completely glitchless so far.