Has anyone used this app?

Yep. Works well in Atlanta, however, with the new kiosks, it takes no time to breeze through customs so not really needed. Interestingly, I did not even use the kiosks two weeks ago. Went straight to an agent and was through in less than 60 seconds.

I have the App, but don't use it. I use Global Entry, but if I did not have GE then I would use the App.

I tried to use it but it wouldn't work, so I have just used the kiosk's.