I fly out of MEM and, although I'm Platinum on NW I *do* occasionally have to fly on DL metal.

The information above is correct, although I have never had an issue with wearing my Bass dress shoes through the magnetometer. Usually the line is relatively short, but I have gone off to "A" terminal to avoid long lines at "B" on occasion. The only moving sidewalks in the airport are used to connect the A and C terminals to B.

Although I hadn't really considered the third checkpoint at "B" security, it's a good point -- why one there and not at the outlet of the other security lines? Perhaps this is because "B" is so much busier, and they think that this will help provide a sort of "check valve" at this busy point?

On the bright side, my personal record for getting from the parking lot ticket dispenser to my gate is five minutes ... and that includes finding a parking spot, walking inside and upstairs, clearing security, and walking to B8.