We have changed planes in Atlanta many times, usually with about 1 hour between flights. For the most part, it is do-able. We usually seem to end up at the end of one concourse and have to get ourselves way over to the other side of the airport, or so it seems each time. Use the "subway" type transportation that is downstairs and it moves you from one concourse to the other in record speed, much faster than hoofing it by way of the moving walkways, unless you have the time for that. Our last flights through there we were late getting in from our first flight, and had to really walk with wings to get to our other flight, and with minutes to spare, got there and the second flight's departure was delayed....but it was better to have hi-tailed it over there than to have missed a flight. I personally like it to be that you don't have a lot of waiting time between flights, just enough time to hit a restroom and get yourself to your next gate and be about ready to board.
I have been given boarding passes at my initial starting airport, that take us through our plane change in Atlanta with gates assigned etc. but be forewarned, when you debark your first leg, check the screens to make sure that the gate assignment is right, or hasn't been changed. We have several times found that what was assigned at our home airport was not the right gate once getting to Atlanta. Just check, it will save you from getting yourself to the wrong concourse and having to get yourself someplace else.