Read the whole thing here. A short quote:
You could learn about the Theory of Constraints and develop a diagram on paper, on a blackboard, or using a diagramming tool such as OmniGraffle; but Flying Logic has some important advantages. It is dedicated to the appropriate kinds of diagram, so its tools and automatic layout and formatting facilitate rapid, accurate diagram construction without your having to worry about presentational details. A diagram is constructed, developed, and rearranged by a series of extremely simple mouse and keyboard gestures; for example, a simple drag connects two entities causally, and the diagram magically rearranges itself to reflect this. Thus you spend your time entirely on content, letting Flying Logic take care of form.