IIRC, once as a pax on either AA or CO back in the '80s.

As a mechanic; been involved in a couple for various reasons. Generally during overnight hours, and ramp service has taken the pushback equipment elsewhere on the concourse.

From experience, doing a powerback is a tricky operation (and can be a tad hair-raising) due to not being able to see anything that might get in the way, and the possibility of a tail stand when applying the brakes while rolling backwards (tip: completely close the T/Rs before lightly tapping the brakes).