We're adopting a more flexible release strategy that is feature/initiative driven, not time boxed. It would be great to be able to generate a burndown chart for an initiative (even better: overlay several initiatives) so we can project/monitor our capability to issue a release at the completion of the initiative, rather than pre-allocate the features/initiatives to a time-boxed release.
At previous companies I have used Jira and loved their Epic reports (Burndown and Epic Report). It would be extremely helpful to have these types of reports for both Initiatives and Master Features/Activities.