Not according to this study by Aviv Nevo at Northwestern and François Ortalo-Magné at Wisconsin. They compared two types of sales in Madison, Wisconsin - ones using real estate agents and ones completed through FSOB Madison. Sellers represented by real estate agents did not realize higher prices; in fact, the prices were actually a bit lower. And this is before the commission is paid.
The one apparent benefit of using a real estate agent? Homes sold through agents tended to sell faster.