This part is a bit concerning, especially given the sudden cancellation of the Visa promotion: "There are a limited number of bonus points available for this promotional offer-we may change or cancel this promotion at any time."
That said, I'll probably still use it for a booking coming up here in a couple weeks; the risk is rather low (I need to stay anyways; it's just waiting to use a free night voucher for a stay later in the year instead of using it now, and I can always cancel if the promo is cancelled a day or two before checking in.) However, I'd be very wary about scheduling a mattress run around this promotion.