Sound extreme? Well, did you ever read the reports of drivers being unable to get their runaway Toyotas under control and wonder "why didn't they just put the car in neutral or turn it off?" I can't explain the neutral thing; blind panic I assume. But I can understand why some people might not be able to turn their car off in a tense situation.
Depending on the make & model of car with a pushbutton starter, it works different ways and it's never as simple and positive as turning a key a couple detents. Some cars require you press the button twice, or maybe three times in short succession. Sometimes it depends on how fast the car is moving or if the doors are open. Other cars require you lean on the button for 2 or maybe 3 seconds. Ever double-click the mouse on your computer a little too quickly or slowly to do what you wanted? That's the sort of easy-to-bungle dexterity some cars now demand in order to turn them off. And leaning on a button for 2 or 3 seconds in a runaway car when your brain is screaming IS IT WORKING?! isn't going to go well.
I would eschew the pushbutton starter altogether in exchange for an keyless switch. It's sort of a stubby plastic key handle mounted on the steering column where the key used to go and mimics the physical behavior and feedback of one while retaining the convenience of keyless entry and start. An example of this is found of cars like the Mazda CX-9 we just had in the CNET test fleet.
Toyota doesn't like that method and instead may take some voluntary steps to address this soon, by changing their pushbuttons to shut off with three quick presses rather than leaning on it for three seconds. Nice try, but still too fussy in an emergency.
At the very least it may be time for federal vehicle regulators – and believe I hate to involve them any further in automotive design -- to require pushbutton starters all work the same way. I don't think pushbuttons will ever have the sure, positive operation of a key-like device but let's at least create some universal driver knowledge of how they work. Such enforced commonality is not at all odd: You'd find it pretty unsettling if turn signals were operated by a stalk on some cars and by a knob or button on others.
This all risks making me sound like the luddite love child of Ralph Nader and Joan Claybrook but it's a matter of safety and purpose: You spend the tiniest sliver of time starting and stopping your car, it's not a big driver experience issue. Until you can't do it when it counts.