Sander Hoogendoorn gave an interesting talk at TechEd Europe 2010, explaining the technique of using smart use cases in software development.

Smart use cases are a solid unit of work in agile projects, supporting easy estimation of software projects, identifying functional re-use early in projects, front-to-back traceability and automated unit testing. 

For more information on smart use cases and the agile software development platform they are part of, see the Accelerated Delivery Platform (ADP) for Agile Development Wiki.