I fly through Atlanta alot and I never book flights that have less than 90 minutes between flights. Here's why, if the 1st flight is even 15 minutes late you're running between concourses. 2nd more often than not the gate you're pulling into is already occupied. I have landed on time and sat on the tarmac for up to 30 mins at a time waiting for the gate to clear. Why they don't just move the plane to an unoccupied gate is beyond me!