Arrived Saturday on JB from Boston. Pulled up to the jet way and deplaned without incident. We did have wheelchair transport for my wife, so we were brought to the manned immigration booth. They also have scanners for your passport, and take a picture of you. Not sure if it is actually a photo or facial recognition matching to your passport photo.
Two people traveling with us did use the new system. They said they had no problem, there were enough kiosks and they were all working. They got through very quickly, and were only a few minutes behind us.
That said, a Saturday arrival at 10:30 AM, and the only large jet in at the time, may not be the best test!