I just checked all of my 11 accounts and realized that I hadn't received credits on any of them. So I called American Express and read them the riot act. First they told me that there were so many people that participated in the promotion, that they were still catching up on the credits. Then I asked to speak to a supervisor, who told me that although the cards were swiped by the merchant on 11/26, the merchant didn't actually process (i.e., submit their batch of charges) until 11/27. So, the supervisore explained to me that it was the merchant's fault that I was not credited, and as a gesture of good faith, she would credit me manually.
This "explanation" did not sit well with me, so I read her the riot act (in the hope of getting some SPG points out of her). I told her (1) that I had received an email from Amex instantly on 11/26 after swiping the cards, which confirmed that I had completed the "necessary transactions" for the promotion, (2) that the promotion was between Amex and the cardholder, so the merchant's actions really have no bearing on my satisfaction of the terms and Amex's obligation to honor its obligation and (3) that Amex made me look like a fool since everyone who I told about the promotion was complaining to me that they never received credit. But she stuck to her guns and said that it was the merchant's fault, and I should just tell everyone I know to contact Amex and request a manual credit.
Needless to say, I'm not impressed with the way Amex handled this, and I'm sure there are tens of thousands of cardholders out there who are not receiving credit because their merchants' credit card charges were sent out in batches the next day. Of course, the supervisor that I spoke to told me that this is first time she encountered any cardholder who was not credited automatically, although she conceded that it's very common for charges to be processed in batches a day after being swiped.