This is one of the best apps I've seen in a long time. The UI is very intuitive, and is quite different from what we have been offered so far in the way of notetaking (backpack, zoho planner). I really like how it provides a simple and quick way to create heirarchical notes. Formatting using any variety of syntax's takes entirely too long to make a good use of traditional text entry.
I'd love to see this style text entry applied to other apps, so that I don't have to go back to college just to take advantage of this one.
I also agree with the Solution Watch review that with it's target market being students, and not just technical students, that there should be some sort of explanation for the site and how it works. I'm a huge fan of role based demos, so it would be great to see a couple "real world use cases" or examples of how a student could use this app.