Some of you may already know that Marriott Gift card/vacation is considered as visa when using at marriott properties and is qualifying for all promotions that require a visa card.
The card has 15 numbers and exp date printed on the back, to use as a visa for prepaid rate on marriott.com, select visa as payment option, add a 4 in front of rest 15 numbers, use exp date on the card as exp date. You are good to go!
I just tried last week, it worked out!
If using at international properties, it carries 3% transaction charge just like most Visa cards.
This will make marriott stay cheaper, because most time you get your Gift Card/Vacation at a discounted price, sometimes 10% off, sometimes 10% bonus, sometimes 10 MR points per dollar, check the promotion I mentioned here.
Also, using your Marriott Credit card to purchase Gift card on Marriott website is considered as marriott related charge, that means 5 MR points per dollar. so, you get 5 points u suppose to get if using the card at properties and you get extra perks/saving by using gift card!