The XML Benchmark Project was started to provide a framework for evaluating the interplay of XML technologies and Database Management Systems. The benchmark lays emphasis on engineering aspects as well as on performance of the query processor. In this chapter the authors present a quick overview of the benchmark and point at some of the experience they gathered during the design of the benchmark and while running it on a variety of platforms. Since the benchmark was designed early in the evolution of XML, our experiences also reflect how the perception of XML changed during the three years that have passed since we started working on the subject. The chapter comprises an overview of the benchmark as well as discussions of some lessons learn...