Sets of "personas" representing archetypical visitors of two very different museums, the Acropolis Museum in Greece and Cité de l'espace in France, were defined and described as part of a multitude of user-centered design methods used to better understand the needs of visitors and develop for them a personalized mobile storytelling experience. Here we reflect on the role and impact that these personas have had, not only on the design process but also as a mechanism to support the story authors and to bootstrap personalization of experiences. We conclude with a discussion of research challenges inherent in the integration of personas directly into systems intended to support the personalization of experiences.