Actually, it's probably between 0.5 seconds for your common driver, if they aren't really in a hurry. I've got timing data that show shift times of 0.1 seconds (or possibly better) are possible with a good driver and a good box.

Older ATs take longer than that to shift, and, worse, take some time to "make up their mind" about when to shift. Newfangled DSGs, SMGs, CVTs and the like have shift times that most drivers can't beat, and some economy cars are getting ultra-fast boxes, too.

I'm pretty sure I could shift a five-speed MT Ranger as fast or faster than the five-speed AT box can, but not on every single shift at every single stoplight. And there's no way I can shift as fast as VW's new DSG (8 milliseconds? I can't even blink that fast!)

But the point isn't the time you take to shift, but how much power you use and how long you use it to get to a certain speed. And therein lies the advantage of boxes with more gears, and the advantage of manual boxes over their heavier, inertia-challenged, torque-converter equipped automatic brethren. CVT's another story, though...