Hmm. Completely brown-out the CPU in between keypresses? I always heard cold starts are very very slow (compared to regular operation). While I guess I don't have a measure for how slow, it seems unlikely that if a user is typing at 360CPM (60WPM * ~7), that you will be able to completely shut off the CPU much.
I'm not sure about the CPU numbers either (though my understanding is that modern CPUs are super-quick to power down and back up), but I think 360 CPM is way too high: few people type at 60 WPM, most words aren't 7 letters long, and nearly no one is typing 100% of the time they're at their computer.
Oh, I agree there is ample opportunity for shutting down the CPU. I probably spend more time just looking at the screen reading, than any other activity.
