I love it! I could see myself using it to document event storming sessions, impact maps, Wardley maps, etc.

That said, I found it a little buggy at the moment. A couple of bugs I noticed were that scrolling too quickly to the right produced an error, and the 'flag' box rendered some of the text outside of the box. A tiny usability improvement for me would be if the buttons behaved more like Photoshop or Omnigraffle, where I can select the tool and then apply it on the canvas, rather than dragging the tool to the canvas. I'd also like to try out all the different tools before paying - the checklist box, for example.