I believe the rebate is given in the form of a Amex Pre-paid card. I've done the rebate deal, and was able to track the progress of it online. They take the maximum possible time to process it, but at least, you can see online that it was received and approved. Then its still several weeks before they send the card.
However, the instant rebates were no bargain, since they were off the retail price. This is a much better deal.