"Early modern Europeans usually sank each evening into what they called a 'first sleep,' which lasted for several hours. Shortly after midnight, they awoke and spent 1 or 2 hours in a 'watching period.' A 'second,' or 'morning,' sleep followed.
"The watching period presented many opportunities, Ekirch notes. People coming out of their first sleep often stayed in bed to pray, converse with a bedfellow, contemplate the day's events or the meaning of a dream, or simply let their minds wander in a semiconscious state of contentment that was prized at the time."This 2006 article from the New York Times points out that diagnosing interrupted sleep as a problem is a relatively recent phenomenon, encouraged by the mass marketing of sleep-enhancing drugs.
Updated 8/24/13: A recent article on this topic: Your Ancestors Didn’t Sleep Like You