Concierge just got me a reservation for 4 at a sought-after restaurant in Tampa on Saturday night. OpenTable didn't have availability and neither did the restaurant when I called. The concierge checked online then called the restaurant and forced availability. He said they didn't want to do it but he made it happen. Not sure what type of leverage AmEx has? Given that it wasn't the exact time and I know they didn't have any availability I tend to believe him. Will definitely keep it in mind in the future.