I currently teach business.  But my background is IT so I'm always looking for cool productivity tools.  This is one for sure !!!!  I map an entire chapter.  At a glance I can see where I am in my course and in my lecture.  Now I've started expanding on it - add an icon to indicate nodes (topics) I covered vs not covered ... another icon to point to a 'class activity', etc.  I sometimes print the map for students as an overview.  Awesome product.  Great job. 

How do you use the icon of covered nodes and not covered ones? Do you move a child node to another parent when covered?