We once had a trip from Indianapolis to SNA with a layover in DFW. I remember that on the trip there, when we scheduled the trip, there should have been plently of time to make the connection. But, in fact, our plane from IND was delayed due to storms in the midwest (our trip was the last week of March), and we just barely made the connection as they were closing the plane. DFW is a HUGE airport, and the gates for a particular airline aren't necessarily close to each other. Same thing is true of MSP and ATL. However, the last time we had a layover in ATL, our departure gate for our connecting flight was right next to the arrival gate for the first flight.
About 3 wks ago, I flew from Santa Barbara to Indianapolis via Denver. Many of the flights from SFO were delayed due to heavy fog, which caused delays in many other flights. I actually like Denver compared to the larger DFW, MSP, ORD, because really you can get from one end of the airport to the other in a matter of minutes, and, in general, they are pretty well organized in terms of gate assignment. There aren't alot of choices on food or other activities, though.
I really hated MSP, but, it may have been because we were routed there on a flight from IND to MCO. It irritated me, because my original flight was a nonstop, and because the flight was twice as long being routed through MSP, and the plane flies directly over IND to get to MSP. It was the last flight I ever scheduled on that particular airline (Delta, I think, but could have been NWA just before their merger).