Check out the video over at The Zbrush community Forums of Z4R2 beta, which is coming this September.
DynaMesh enables you to explore multiple concepts in a very short period of time. You do not need to create a base mesh to fit your target-concept, or even have a specific concept in mind. You may simply select a sphere, activate DynaMesh, and let your creative juices flow! It is exhilarating to freely reshape the mesh and quickly explore many ideas until you arrive at a concept worthy of progressing into finer detail.