They're really taking a gamble with everything, but there's not use denying that this is a HUGE PR stunt as well. Their philosophy on game-making is almost populist. From everything I know, they earned a lot of brownie points for that. For them, I honestly hope it works out. My problem is that I won't play this game unless I beat Witcher 1, and that game really isn't too attractive at many points for me. However, I may grind through it just to buy Witcher 2. They're ambitious, and that's definitely worth supporting.
I really think (and hope) that this game will actually be bought more than pirated, both for their sake and in order to validate the beliefs real gamers hold in high regard (unlike those guys who pirated Crysis 2 a full month before its release).