Well, after my experience at DFW on 7/29-30 - have to put my money on DFW as one of the worst.
Never would have said that but, the way you now have to navigate from landing to immigration, to the wait for luggage to customs, to re-checking baggage to finding your way to going through security to you connecting destination - means you most likely will miss your ultimate destiation that day, unless you have more than 3 hour layover. This didn't used to be.
This lesson has reminded me, if I don't have a long layover, plan to stay over night at the connection point. Sad that it takes 2 days to get to somewhere within the same hemosphere.