Mommy Points has a very thorough post on this from last night.
I’m not a Marriott guy but this is a great deal if you have a trip coming up. Essentially, the gift cards are 10% off as part of the Daily Getaways that start today at 1pm EDT. And, you get another 10% off by paying with any AMEX card.
I don’t expect these cards to last long. Most of the Daily Getaway stuff sells out in minutes. Good luck!