Kathy Sierra’s Don’t Make the Demo Look Done provides excellent advice for conveying the state of a project while presenting the project’s functionality. It also discusses advantages such as improved user feedback. With a very rough presentation, users will be comfortable providing inputs on significant system features rather than the particular fonts used in the mockup, for example. The article also mentions other problems that are created by misrepresenting a project’s state.
I have read several software engineering books, and they all discuss requirements acquisition through the use of mockups. Books warn of client confusion when project estimates that are given by software engineers surpasses their expectations. After all, the system seems practically complete after they have seen a polished mockup. Making sure that a client understands that the mockup does not represent the project’s level completion is one way that some books suggest to avoid surprises. Sierra suggests that mockups can be used to give clients a better grasp of the state of the system being developed.