Maybe you could elaborate more on your use case of writing a blog post: Does your app output formatted html that you paste into your blog editor? Do the entries become published pages?
Do you use a UI framework, or are the screenshots just mockups? Either way, they're quite nice!
Well you could use it for anything where you need references and annotations near your content. For instance, you could be writing speech, and you could keep your references in comments, or you could use it for simple manager of your contacts, with each comment being a summary of your conversation. It's pretty flexible, and I want something more powerful than Notepad, but still simple to use.
One other use is writing down of martial arts techniques. You can write the technique down, add videos and pictures of technique that you found on the internet, keep log of your progress in comments etc.
Edit: I plan to create as many export formats as possible. Also you will probably be able to create public version of page.
