edit - let me piggyback a relevant question - if I were to purchase marriott giftcards with my marriott visa card (from marriott.com or anywhere else), would i get the same 5 pt bonus per dollar as I would if I was paying a marriott hotel bill with my visa card?
If you purchase the gift cards on marriott.com and pay with the Marriott VISA, the purchase (in the past, at least) has earned the same 5 points per dollar from the credit card as if you had used the credit card to pay a bill at a marriott property. I don't think it would work that way if you bought the gift cards from another source (like a drugstore).
Also, of course, the charge to the Marriott VISA goes toward the free night credit for each $3,000 charged to the card.