Our teams are prioritizing Epics, not just Stories, to allow us to develop and document a highere level plan that covers more than 3-4 Sprints.  This prioritization can be accomplished by moving Epics above and below each other in the Team Board where we manage the Stories.  However, it is very difficult to re-order a number of Epics because the width of the Epic panel is fixed.  If there Epic panel were resizable, like the Story Detail panel, it would be extremely useful.