It seems to be fast enough, and not too difficult to figure out. I don't think it's intuitive enough, though. A login with Facebook (or Twitter), I think, is becoming crucial. Also, a new way of thinking about ToDo lists, would make it a little more appealing, such as a 4 quadrant list based on a vertical scale of importance and a horizontal scale of urgency: http://www.mindtools.com/pages/article/newHTE_91.htm
Also, I think if this was tied into something people are already using, such as Evernote, you'd see more usage potential.
can you start with some dumb-downed obvious places, and slowly work up to harder and harder to recognize? Even something as simple as Statue of Liberty or Mt. Rushmore would be a good introductory... IMO
Also, I think if this was tied into something people are already using, such as Evernote, you'd see more usage potential.