Mobile end users usually work in complex and hectic environments, consequently for mobile e-Business applications the design and development of context aware, smart, adaptive user interfaces is getting more and more important. The main goal is to make the user interface so simple that the end users can concentrate on their tasksnot on the handling of the application, the main challenge is its adaptation to the context. A possible solution is smart adaptation. Consequently, developers need to know the limits of both context and systems and must be aware of mobile end users different interaction. In this paper, we follow the hypothesis that simple user interfaces enhance performance and we report about some lessons learned during the design, development and evaluation of a smart, adaptive user interface for an e-Business application.