Transferring from the D gates to the B gates in an hour is a nightmare. You take the sky train to the next building, get dumped unceremoniously into a vast common area that doesn't have very informative signs directing you to the gates, and every inch of the floor is occupied by people trying to hawk useless junk. Most of the airport has the feel of a gigantic mall. If you are flying to Vegas, it's okay, because you're not trying to go anywhere but Vegas. If you're trying to get home and your connection is through Las Vegas, try to get flights that connect in the same section of the building.
And, how the hell did the Mastercard hawkers get past the security gates? Does the TSA just let these people set up a booth in the gate area? No, I don't want your fucking credit card!