The new elite security line after you clear customs in ATL is indeed new. I can't put an exact length of time it has been there, but i believe it has been there since about the beginning of 2008. It probably also coincides with the renovations of parts of the customs area (the walkway you pass through after handing in your I-95 declaration card).
Personally I think it's a good idea - at the worst times the security recheck area to enter the US in ATL can be a real horror show. To provide A,J,D,I,C class pax and Medallions a special line was long overdue.