Data point: booked Hilton Amsterdam for two nights with the Amex portal. After the $200 credit (before the $100 spa/restaurant credit is taken into account) and around $40 in property fees, my total cost will be $311. The same room would have cost me $472 on Hilton's website (no mention of the $40 in extra fees). Worth it, to me. Now, I probably would not have looked at this hotel if I didn't have the Amex benefit, but either way it's not a terrible deal.