Take a look at it - it's simply a great tool for agile developers.
We started to use it few weeks ago, and, even while there is no good result from the point of planning and predictions yet (at least for DataObjects.Net project), it is really useful anyway. Its main benefit for me is that I'm always know what's important right now \ what are the tasks I should spend my time on. When you take part in a set of projects + have certain amount of correspondence, it isn't always easy to do this. Finally, it's quite easy to re-arrange the stories there and see what happens.