That will be a great feature to use when we decide to go. I have a prepaid Visa (Wachovia Buxx card) that I can link it to that I will be putting $1000 on for our trip. That way, I don't need a lot of cash either.
Guess it wouldn't really matter if I use the room key or my prepaid visa. If I use a room key, it will still come off the card, but then I guess I wouldn't have to carry the card around with me.