We did last Oct. It was kind of goofy though. We had to put our CC on file for charges (which we always do). Then we had to go to the front desk to have them swipe the rewards card instead of charging the credit card. they can't put the rewards card on file like they do a CC.
I think they said accounting automatically charges the card when you hit $500 (I don't remember for sure if it was $500). We had like $750 on our card, and usually charge over $500 on our trips (we charge everything to the room - all food, souvenirs, etc). So we had to go to the desk to do an interim charge on the rewards card during the trip. Otherwise, I think they said just to go charge the rewards card the night before your checkout day.