A user should be able to sort stories in the iteration taskboard so that the most importat story is the topmost.

Every story should have different priority, so how about implementing drag-and-drop sorting?

For example, in Scrum methodology it is important to start from the most important story and then continue to the second important and so on (simplified explanation). When tasks move to right (done or testing and after that done) starting from the top its easy to see (visualization is important) that the project team is really doing the most important things first.

This is the only reason why our team is considering other agile project management tool.