Originally Posted by
flatlander
Definitely use the machines. They should match your fingerprints to those on file for your current passport (from previous ESTA), then check that passport has a valid ESTA, then let you though. Even if they don't you've dodged most of the queue and will get processed manually.
Exactly. Even if it fails, you will be be sent down a short line to the booths, rather than right to the back of the general population line.
My boss needed a new passport, so needed a new ESTA at the start of the year to replace the old one he was using to travel to the US, and the machines let him through without a problem.