US Immigration and Customs are efficient and normally quite friendly. Airport security is thorough but friendly and efficient as well. Terminal transfers via the overhead train system inside security is wonderfully easy. I have gotten stuck at DFW for hours at a time because of cancelled flights on several occasions and there is no better place to be. In Terminal D there are ample restaurants both fast food and real food which are quick and good. There is lots of shopping and things to do while making time. No free wireless internet though just paid via T-Mobile. Other terminals also have decent restaurants and shopping but you can always take the train to terminal D if time permits. Baggage claim and ground transportation are a breeze as is parking if you have to drive there to pick somebody up. Check in is just as easy and convenient because of the terminal layout.