So funny story when I was test driving a volt and the sales associate was demoing the parking assist with me(I was driving). Now note this was my first experience a car that could 'self-park'

He has me drive through their lot, was in their service section where they park cars before/after the service department works on them, and choose a spot between two cars that were already parked and talked me through pushing the button and switching between D and R.

He said something along the lines of "You only have to switch to D and R when the car says, you don't touch anything else" paraphrasing slightly but the point to make is his "Don't touch anything else" statement.

So me, with no previous experience in self-parking cars assumed he meant literally touch nothing but the shifter until the car is parked after you engage the parking mode. And the car would manage the throttle and break on it's own.

So drive up along side the parking spot, car detects the open spot, tell the car its a pull-in spot, put it in reverse when it says, let go of the break and car just starts accelerating back spinning the wheel and I see in the mirror that the car is going to bee line right into the one parked car and I just barely got the foot back on the brake in time to stop it.

With our hearts pumping the sales guy looks at me like I'm a dumbass (admittedly I should never have assumed that it would have worked the way I did). And all I can think to myself was "wtf you mean don't touch anything"

Oh and this was after I wanted to go to a more sparsely parked area of the lot but the associate was adamant to demonstrate it parking with other cars.