I've been using MindNode for this.

I've found it very good at letting me quickly transfer my system ideas to paper. It gets out of the way and works with quick keystrokes.

But it breaks down when trying to use it for presentation. It is too difficult to show and hide different states of the system when presenting to others. It's slow changing between each state by showing and hiding different nodes.

I'm looking forward to trying your tool for this reason. I just wish it was a local program.