From CBP website: Instead of filling out a paper Customs declaration form, eligible passengers can proceed directly to the APC kiosks in the passport control area. Travelers are prompted to scan their passport, take a photograph using the kiosk, and answer a series of questions verifying biographic and flight information. Once passengers have completed the series of questions and submitted their Customs declaration form, a receipt will be issued. Travelers then bring their passport and receipt to a CBP Officer to finalize their inspection for entry into the United States. The kiosks allow people residing at the same address to be processed together.
So it differs from GE in that you still have to talk to a CBP official for immigration and also go through Customs (handing over the form is typically the most this involved) while GE members go to a kiosk and unless we get an X on our slip we are basically done. We get our bags and hand the slip over and are out the door. The CBP kiosks are an improvement in handling, in my opinion, but not nearly as convenient as GE.
I'd recommend also looking into GE for the future. For you two returning to/visiting the US in the future it will make things much easier and as a GE member you can also apply to the UK program which allows GE members to use the EU lines at airports in the UK. Maybe doing the interview on the return if you have time at ATL.