I've used it a few times and found it generally useful (although I've struck out with this benefit too, in that they claimed "extraordinary demand"). Sometimes I've used it to get reservations at a property that was showing up as sold-out on hyatt.com but that had rooms available on Priceline (i.e., the room was still available but apparently pre-sold) or for (I think) awards but not for a Hyatt-sold paid rate.