Scrum Master – Have fun with Burndown Charts

Since several sprints I have paint it some Burndown charts they can inspire you to do so.
Burndown’s can help your team staying focused on the sprint backlog.
It also shows you up, if you have too big stories in your sprint, because they take more time to getting done.
My recommendation is not count the Subtasks, only show up the real burned stories.
What are your experience about burndowns?