I would have at least switched rooms before moving. They might have put in 100 new mattresses at the same time, but they were not 100 identical mattresses. Some were firmer than most, some a little less. I find it rare that Marriotts have mattresses that aren't firm enough, usually its the other way around. Regardless, if your beef was with mattress in the room and nothing else, then a room change or least a quick test drive of another, available room's bed would have been the way forward.