Profanity: If you do decide to buy it from steam, you should know that at the moment they don't have any keys for the game, so you'll have to wait until they get more keys from Rockstar which probably will be at the end of the sale, I guess. Maybe a day after the sale, who knows.
Oh, and apparently quite the number of people who did manage to get the codes, before steam's vault was emptied, have trouble activating them. So it'll probably be iffy to get it running + the waiting for whenever Steam gets more keys.
Anyway, thought you should know.
Thanks for the info and thanks everyone for helping! I bought the game from GamersGate.