It would be nice when in the preferences a maximum heigt can be giving to the node. Now it is just as big as the text is and that makes it difficult to navigate the mindmap when one or more nodes are open.
When the text is larger then the maximum height a scrollbar will appear. Much like the edit long node screen but the in the mindmap (and without the buttons of course :-)
I like the idea of a 'final' node on a particular branch. If you could flag that a particular node could produce no children (...sterilize...) it would be cool.