I've read anecdotes about people who solve technical problems in their dreams and the concept of getting a few more mental hours out of the day is very appealing.
This is one that every russian kid knows from school days:
"I saw in a dream a table where all elements fell into place as required. Awakening, I immediately wrote it down on a piece of paper, only in one place did a correction later seem necessary."
—Mendeleev, as quoted by Inostrantzev
http://en.wikipedia.org/wiki/Dmitri_Mendeleev#Periodic_table