Here is an interesting summary article about the importance of sleep and our health. The author discusses how sleep affects memory, the endocrine system, the immune system, and psychiatric disorders. The author uses quotes from a Harvard sleep researcher, Dr. Stickgold, who explains some of the recent findings about sleep and health.
I thought his description of dream importance was a little confusing. In the beginning, he suggests dreams are "much, much less important" than once thought. Then he describes how dreams help us remember and organize recent events. Perhaps he means dreams are less important with regard to analysis of the unconscious?