Yes, passengers whose final destination is Atlanta do have to go back through TSA screening, and here's why:

ATL's success as an airport (it's the busiest in the world) is in part due to it's "all air-side" design". So passengers with connecting flights (domestic-to-domestic or domestic-to-international) never have to worry about being held up by any sort of additional screening. Once you're in the gate area you're done. The original international arrivals terminal at ATL was the T terminal. It's smaller than the others, and it's immediately adjacent to ticketing and baggage claim, and therefore has direct access to the street.

The E terminal (now international arrivals) was constructed for the '96 Olympics and is much larger and generally works pretty efficiently, but because it is the farthest from the street there's no way to exit the terminal and then go directly to your car or ground transportation.

This problem is being addressed with the construction of street access to the E terminal (and I think also some nicer arrival facilities) although I gather that the economic crunch has slowed things a bit.

As a long-time resident of Atlanta I consider the extra TSA screening to be a reasonable trade-off for the overall smooth operation of ATL. Were it not such a great place to connect, we (me and my fellow Atlantans) wouldn't have access to so many great flights.

Oh, and the reason that you have to be re-screened at all is that you've access to your checked luggage while going through Customs (when you are technically land-side, not air-side), and could potentially have moved a dangerous item from that bag into your hand luggage.

CarolA, you checked a bag? ;-) Aren't you the one with the pink carry-on?

I did check mine when returning from Asia is January and did actually have good luck with Delta's priority tag: it was the first bag off the plane at the international terminal.

But once it was re-checked to be claimed in the South Terminal baggage claim it was just a regular bag.

My opinion about what happens at ATL TSA international arriving screening is that it is a combination of problems:
1. only up 4 or so lanes, which can back up with several jumbos land at same time.
2. folks aren't expecting the screening so they aren't prepared--they took their liquids out while on an overnight plane, so they aren't in the plastic bag.
3. folks are arriving from different countries with different screening rules, such as they don't remove shoes and jacket at screening in their home country.
4. people are tired and stressed about where their checked bags just went to and where their connecting gate is.

Last few times I arrived at ATL there were short lines at immigration, customs, and TSA, so I sailed through, but other times I've had to wait for bags and stood in a long ling shuffling through customs, immigration, and TSA--a function of how many planes arrived at same time.

The customs beagle keeps getting fresh. I often have a backpack and the handler lets him/her jump up to take a sniff without warning me.