I just timed my Wii U's boot up (literally, gamepad in one hand, stopwatch on phone in the other) and it took ~20 seconds from pressing the power button on the controller to main screen.
I don't get this. Maybe because I have the normal, white bundle with no HDD connected? If they reduce it by 20 seconds it will be instant-on
Yep, i got the same result when i was bored one day and timed boot times for my 3 consoles. About 20 seconds from power to having control.