Quoted from bingopodcast:

Most bingo pinballs are far more complex than anything mentioned. The most complex of these is Bally's Hawaii, which I suspect is also the heaviest EM pinball. Some of the complexity (if doing coil counts) is hidden because of the clutched control unit and mixer unit.
Grand Prix is one of the most irritating to work on, though! The position of the relay bank under the playfield means that the bundle can be caught as the playfield is lifted, tearing wires. The bonus stepper near the front of the playfield is unfortunately in a perfect position for someone to set it down on, causing improper indexing. The match unit pulls so many duties that it creates a lot of problems if it is not moving properly.
I've only worked on one OXO but I don't remember it being nearly as irritating. Maybe that's because I've worked on so many different Grand Prixs.

Quoted from bingopodcast:

What defines pinball to you? Plunger? Pins? Rubber? Posts? Balls? A playfield in a cabinet at an incline? Game rules?
These are of course all present in bingo pinballs as well.
The player has quite a bit of control, unlike a slot machine. In some ways, much more control than flipperless amusement pinballs.
All coin op machines were made to take your money.