I used it flying into Boston earlier this year. We came in after at least one South American flight, so the non-ESTA line looked to be about three hours long. The ESTA line looked about two-thirds of that. (That was a LOT of tensa-tape.)
GE had all kiosks occupied, queue of three/four people.
With MPC, I went straight to a desk “oh you gotta photo!” Said the agent. Two ticks later I was on my way.

When the system works, it works well.