Its been a few days since I placed my pre order for 2K10 and I still haven't gotten the email about the $10 gift card. I guess I would have to wait a bit more like Interfaci (in nor real hurry as I plan to purchase MW2 next). Will report when I receive my gift card.
Except... It doesn't work like that. You have to wait for them to physically ship the game to get your credit. "The promotional code will be placed directly into your Amazon.com account within 2 business days after the product ships." They're pretty clear about it.