Interesting article:
http://blog.bufferapp.com/how-much-sleep-do-we-really-need-to-work-productively
Highlights:
"The sleep deprived person can in fact deliver the exact same results as someone who isn’t sleep deprived in any exercise. That is, given it is a non repeated exercise and they give it their best shot."
"The problem lies elsewhere...The main finding is that the brain of the sleep-deprived individual is working normally sometimes, but intermittently suffers from something akin to power failure."
"For the highest quality of sleep, you need to be drained, both physically and mentally to some extent."
Real interesting stuff.