Entering at BOS this past week it was the fastest and smoothest GE entry for me - 5 seconds at the machine (scanned my face successfully with my glasses on), just waved through by CBP officer after cursory question about anything to declare. (Did not have to present passport.)

Happened to glance at officer's screen as I walked by - it looks like the screen shows id pictures of about 10 people at once, presumably those who have gone through the facial scanning or otherwise interacted with the kiosks and are waiting to walk up. Presumably that's enough for the officer to visually match the person walking up with one of the pictures on screen, and no further details need to be verified in most cases.