In the paper, Adding Usability Testing to an Agile Project, Gerard Meszaros and Janice Aston, of Canadian Pacific Railway, describe the injection of paper prototyping and lightweight usability testing into their project. Gerard has explained to me that after injecting the practice, the amount of rework they normally saw after each release went down to a fraction of what it had been. And, business stakeholders and users are more actively involved and engaged than ever before.