I'm trying to figure out exactly how GOG sells it's games.
Is it just that you recieve a Game key and instructions on how to download the game from the distributor or through Steam or whatever else? I'm somewhat confused and it's making me hesitant to use this site. (However pretty it may be =P)

And I'm mostly asking for the purpose of Witcher 2. Can it be used in conjuction with Steam? Achievements and all. Do I get a Steam key?

EDIT: Sorry if this is ridiculously newby =]

You download the installers and game files directly from gog.com. Once you purchase a game, the link to the download files and any extras that come with it appear in your 'My Account' page.

As for Witcher 2, you do not get a Steam Key for it or Steam Achievements. You do however get a DRM free version of the game. That is the trade off.

This site doesn't sell Steam keys for any of its games because Steam is DRM and GOG sells DRM-free games.

Edit: if you want to check how it all works grab one of the free games like "Beneath a Steel Sky" and check it on your shelf.

Have you seen your account?
You have a shelf.
You purchase game and it goes on your shelf.
You can download from your shelf through the browser or by downloading the downloader.
Games stay on your shelf and can be downloaded again at any time.
This is not Steam in any way. NO!
The website explains as you go what to do. It is pretty easy.
Look around the site and community and you will see how this site is truly different.
Enjoy.

See, guys?
I'm not always a dick.

EDIT: GOG trusts you when you set your location so if you don't want the edited version, change your location!

when you buy the game it registers on your GOG account. the option them becomes available to download, all files are downloaded and once they are on you machine run the installer.

Once you purchase a game you have to gather nine companions and travel into the east to the lands which lie under the shadow. Halfway, your companions will part from you. You must be:
a) Mentally prepared to face the challenge alone
b) Physically able
c) Deeply spiritual

You will know what to do when you reach the shadow land. But it will be tough. Only once you have learned your purpose will you receive your game.

Good luck traveller.

There are some free games here to test it out. Add them to your account and then take a look into your account. You can use a downloader or use directly the browser to download them. Some bigger games are split into some files for easier downloading. The same way it works with bought games.

http://www.gog.com/en/catalogue#all_genres/price/0/

Stop. Who would cross the Bridge of Death must answer me these questions three, ere the other side he see.

CDProjekt has stated that all DLC for the Witcher 2 will be made available for free. Though I believe you do have to register a CD key with the Witcher 2 site. The CD key is emailed to the email you used to register your account here.

This is easy... you get a Serial Key for Witcher 2 that you can register with CD Project RED. With this registration, you can also buy DLC.

All current DLC are already bundled in the 1.2 Patch!

Let me add that as of right now all DLC has been included with patch 1.2 so registering the key isn't even required to get it. If they release new DLC in the future it should be gotten from the game launcher as it was intended initially.

Okay one final question which... I don't really expect an answer for... but I'll ask anyway.

What if I have a copy of Witcher 2 already that I got from, let's say a friend, that was not purchased, rather downloaded for free from some dubious sites.

The save file I currently have on it, would it be able to be used with the purchased version.
Yes I fully intend on buying it, which is why I ask all these questions.

As noted by hobbes, DLC is free. No need to buy. CDPR has stated DLC will be free for the game, so there should never be a need to buy it. ;)

Almost certainly. At the very least - I can't see a reason why the game would refuse to accept it, since there's no DRM so it greets everything with open arms... just like us :3.
You might just post the save and someone here who has TW2 installed might try to load it, of course...