Short naps have been tried, tested, evaluated and found to be beneficial (there used to be quite a bit of interesting info at NASA's Ames Research Centre website).
I've seen some new articles out recently in HF circles suggesting concepts of "Sleep Inertia" which basically suggest that depending on the individual, the circumstances of drowsiness and the time spent dozing can be detrimental to performance .... Why? Because depending on what point in the sleep cycle the individual was just prior to waking the "lights maybe on, but nobody's home". For periods upto 40+ minutes the effects of sleep can dog the individual - it's the "I'm never fully awake in the mornings until I've had my cup of coffee and read the front page of the paper" syndrome.
Just food for thought ...
