Denver Airport
It took me 13 minutes and 20 seconds to walk from one end of Terminal B at the Denver International airport to the complete other side. At a normal walking pace and not using the moving walkways.
Using the moving walkways I was able to walk from one end to the other in 8 minutes and 50 seconds. A 4 minutes and 30 second differential, which is a 33% improvement. I think the walkways also stimulates your pace being picked up. Future experiments will be needed to confirm this hypothesis.
A more common scenario is the following test I performed: You arrive at the halfway point of the Terminal and your gate is at the end. For this test I used a hurried pace and the moving walkways and was able to achieve a 3 minutes 55 second time across half of Terminal B.
Please note: your timings may be different based upon your walking pace, the size of your luggage and the number of inconsiderate people who believe the moving walkway is a Disneyland ride.
All timing by a Swiss Army Watch which coincidentally was purchased during another fit of boredom at the Denver airport on a different 5-hour lay over.