Hello Don,
thank you for this beautiful and extremely useful software. This is an enhancement request: 
would it be possible to insert a modifier key in order to have bubbles automagically align on a 
vertical, horizontal and/or some 30°/45°/60° setting?
It would help to organize in a visually appealing way thoughts that are "linear", i.e. one after 
the other, instead of having them connected by an all broken line.
It could be done, for example, like this:

1) Click and create the new bubble
2) Fill the bubble
3) Move the newly created bubble holding the shift button and have the connecting like 
toggling between 3/4 fixed positions.

Oh, and I second the idea of exporting SVG: it would be great to create publishable content.
Again thank you!