Once it is enabled, this App adds a new up arrow icon on stories and story details. Every authenticated user who has access to the project can vote (or revoke their vote) for its stories until they are planned.
The Product Owner can sort the Sandbox and the Product Backlog by votes in order to get a good idea of the popularity of new stories, e.g. from the stakeholders and end-users points of view.
While it is obviously not enough to decide how the vision and story prioritization should evolve, this can greatly contribute to the business knowledge of the team and thus help increase the value delivered through your product.