Thought I'd add my experience of GE interview on arrival a couple of weeks ago. I am a UK citizen.
Arrived into Denver 1st off the plane so no line for immigration or GE was seen.
Mentioned that I was looking for interview on arrival and was directed down a separate line.
I was asked how many banks I had robbed, my wife was asked if she was planning on causing any trouble and that was it.
Very quick, friendly and no hassles.

Used TSA pre-check lines departing back to UK from Phoenix and zipped through security with no line or waiting.