there's a moving walkway between D & C, C & B and at least one in the A complex over ticketing. It's still a hike, though.

It was an easy 10-15 minute walk for me when I went for my Global Entry interview. I was walking from E and I'm a pretty fit guy. The only quick way to get across the airport is to get a ride.

Just make sure the car has a bell (they use the little bike handlebar ringers we had as kids) other wise the driver will stop every ten feet to let people walk in front of the car....