Why Flatland?
You want well laid out, human readable diagrams.
But you don’t have time to push pixels around every time you want to edit your models.
You want to put your models under configuration management and use your favorite IDE–diffing, folding, global replacing, etc. just like a real software engineer.
You want to know if a change to your model was actually a change to the model itself or just a tweak in the layout.
Someone contributed a new Blueprint app, like a logic validator, and you want to feed your models into it.
You type a LOT faster than you can drill down through menus and drag rectangles and arrows around.
And there’s nothing stopping anyone from contributing a slick GUI on top of Flatland.