We just came through there last week on our return from CSS. The lines were not bad at all, getting your passport checked, there were plenty of open windows so that there was maybe 2-3 people in each line. Once you get your luggage and drop it back off, the line to get screened (whole body scan and carry-on xray) was about a 20 min wait. It probably depends on the time of day, our flight landed in ATL at about 6pm. Hopefully you have more than an hour inbetween flights. There were some people in line near us that didn't have a very long layover, bad idea when having to deal with CBP.
we came back late afternoon Saturday May 11th (Delta) and there was no one but our plane/people in this area. We were through so fast that we had to wait 20 minutes for luggage. I did not notice any lack of personel in customs.