score:5
Like most airports the time to get through immigration at DFW is variable, and depends mainly on what other flights land around the time your flight does. As a non-US citizen I've passed through immigration there in minutes, and I've also spent over an hour in line - and you'll find reports of people waiting even longer.
There are no special lines for connecting passengers (Washington Dulles is the only US airport I can think of that has this, and it doesn't help - like DFW, most passengers are connecting!).
There is a bag-drop immediately after you pass through customs. Presuming you have a boarding pass for your onwards flight you can then re-clear security in the same terminal (terminal D) and catch the train to the terminal you're departing from. If you don't have a boarding pass you'll need to catch the land-side bus to your terminal, check-in and then pass through security.