We present the results, experiences and takeaways from comparing a diverse set of dynamic spectrum access methods during the IEEE DySPAN 2015 spectrum challenge. Five solutions for coexistence with a given wireless link were implemented and tested in an unknown environment during the conference in Stockholm. The challenge was framed broadly, enabling participants to use their own hardware, antennas, physical layer or medium access control solutions to compete in a unified setup. Each solution was ran two times and ranked using a single metric. Between the two runs the teams were allowed to improve their solution. The metric considered wanted throughput and unwanted interference. In addition to the metric, all solutions were evaluated by a jury. In this paper, we give a detailed overview of the challenge, how we organized it, the participating teams and finally the winners. We conclude with some takeaways on dynamic spectrum access.