I used it for the first time last week at JFK Terminal 8 – it was a big improvement. But as has been said, its usefulness remains dependent on the queues – for the machines and for the immigration officers. In my case, there were no queues for the machines (this will no doubt change as more visitors cotton on to the possibility of using them) – and only a short but initially slow-moving queue for the immigration officer – though soon after, someone came to specifically to process ESTA/machine passengers and we went very quickly through.
My only challenge was getting it to read my passport – normally don’t have problems with any other automated passport reader I use, but did need to call over a member of staff to help me get it read.
They were announcing that first time ESTA visitors couldn’t use the machines; I thought I’d try my luck – it wasn’t my first time, but it was the first time on that ESTA (my third) – and all worked smoothly.