When I need to draft a document that shows visual objects and relationships (e.g. architecture diagrams), I jump into OmniGraffle. The reason that this is my tool of choice is because the input mechanism is mainly through an outline tool. I can very quickly jot everything that I need to say down into an outline format and OmniGraffle will automagically try to align everything for me. Only then do I start to drag things around.
So, my feedback for this tool is to make input much easier. Instead of "click, type, move" over and over again.. smooth that process out by having a type-only input mechanism.