The app looks fantastic; looks like it will answer all my dreams for drafting academic papers.
However, it's currently almost unusable. I loaded up one of the example documents, and the app hung for minutes at a time for pretty simple interactions. I started a new document, and tried to import my bibtex library (since I don't have Papers). Beach ball, and I had to force quit.
As I said, the app looks great and I can't wait to be able to test it out. But I think you need to work on fixing some basic usability bugs before it's ready for prime time. I can't evaluate whether or not to buy an app if I can't interact with it.
If you want some technical details about my (pretty standard) setup for a detailed bug report, I'm happy to help out.