cdkeyhouse

I'm of the opinion it's best to never touch key sites unless they're real retailers like Gamersgate and the like.

Those key sites generally buy a whole bunch of keys from cheaper regions (such as Russia) and resell them. This can lead to problems like having to use a vpn to activate the game, there's also the chance of the key being flagged and having Valve closing your account/suspending it.
You'll also find they will sometimes sell the "exploited keys" (serch Dirt 3 to see the mess with that) which again can have your account flagged by Valve. They also have some pretty terrible user agreements (look up Intkeys and look at their agreement, hilarious) where they take pretty much 0 responsibility if Valve does shut down your account.

All in all, not worth it just to save a few bucks on a game.

I like my steam games to come from steam

Totally legit, bought multiple games off of it for such great deals.

This its actually referring to the webpage you linked btw