I will tell you what we learned the HARD way last year:
Terminal E has NO CURBSIDE baggage check for AirTran. Early in the morning there are NO PORTERS and NO LUGGAGE CARTS!!

The parking shuttle dumped us on the sidewalk and we had more luggage than we could carry. With American there is ALWAYS curbside or someone to help you!
We got upstairs and there were NO SIGNS to show where the AirTran desk is.
We checked the bags and there were at least 200 people in the security line in front of us. They were operating ONE, yes ONE, archway to screen people.
I am one of the meanest girls you will ever meet and I never cry about anything, but that experience had me in tears. I KNEW we were going to miss that plane.
We sprinted to the gate barefoot and made it with about 3 seconds to spare before they shut the door and pushed back from the gate.
Having said that, we are flying them again on Friday. We are leaving the house about 3.5 hours ahead because it was such a nightmare last year. This year we know what to expect so we will be prepared.
I have nothing ugly to say about AirTran, it is the way DFW has chosen to handle AirTran's customers. Get there EARLY and don't bring more luggage than you can take to the desk by yourself.