Interesting snippet in Wired this month - 3 Smart Things About Sleeping in Late. Also the reason why an early start in the office should be 9:30! We all need more sleep than we think - so spending more time under the duvet is good (have a read of Guy Claxton's Hare Brain, Toirtoise Mind). You are more creative at night - so nobody should ever be made to do an 8am meeting. Rising early causes more stress (all to do with the production of the hormone cortisol).
So stay in bed. It's good for you.