I like the app and I think the easy to remember name suits it well, even if Hemingway might turn in his grave. It's a promising start, but I'm not sure if I'd continue to use it unless I could start tracking improvements in my writing.

I would love to see a bit more of the hard data behind the rankings. For example, I just tested a blog article I wrote 5 minutes ago against an article written by a proper journo on PandoDaily and I scored higher. Does that make me a better writer? I hope not.

In all seriousness, the idea has a lot of potential and you could certainly find a few nice ways to compare yourself different writing styles of famous authors Hemingway or someone else.