I used the kiosks in BOS yesterday for the first time and found it to be pretty convenient - the longest part of the process was waiting for the kiosk to elevate itself so that the camera could get my picture since I'm on the taller side...at the immigration inspection point right after the kiosks, I was only asked two questions from an incredibly bored-looking CBP agent...

"Where are you coming from?"
"What were you doing there?"