A 15-20 minute power nap can be a beautiful thing. I try to get one in at lunch time every day, if I'm feeling a little tired. It can be very rejuvinating, recharging you in order to finish out the day as strong as you went through the morning.
However, there is a danger. If you happen to oversleep, say, by 10 or 15 minutes. That turns a recharging power nap into a draining endeavor. You wake up feeling sluggish, and are a half step behind for the rest of the day. Often this results in a follow-up nap after work (those with kids probably can't pull this off) which may or may not help in getting over the lethargic feeling.
Nappers beware! While a quick power nap can be just what the doctor ordered, taking it too far can be counter-productive.
The More You Know...