I love alternative to-do approach and loathe David Allen's crazy GTD method (after having tried to implement it for years) but there's one problem with this app:
It will not scale. I can say that because having input 5 tasks, I already feel ambivalent as to what to do, and what's most important. Imagine having input several hundred tasks into thirty projects or so... I get stressed just thinking about the mayhem that would visually be presented to me.
The ideal to-do manager would be an app that helps you cut down on all the mess and competiting tasks.