We did it at FLL and were taken on time. Thirty minutes later we were on the way home. I also had trouble with my fingerprints but they said its quite common.
We used it in Miami on our way home from Paris last summer and it was so fast. If there are any problems at all you go to the front of the line. There was a TSA agent at the kiosk helping.
Will be trying it again in March in Newark on the way home from Hong Kong.
The best part is no customs!!! We just walked out the door.
