As a David Allen enthusiast, I really wanted to like this app... and it has some great things going for it: one window lets you sketch out your projects and a separate window lists all the next actions of that project in their own "contexts" (at home, at work, online, calls, etc.) without the project hierarchy cluttering up your thinking... this allows you to focus on your next actions and so not even think about why you're doing them, which is the essense of the David Allen GTD system, to free the mind from thinking about too many things at once. This feature alone makes this a great product.
I did, however, find several UI problems:
1) the button navigation was not very intuitive (i.e. the up, down, left, right arrows), as they are, say, in in OmniOutliner (note: OmniOutliner is not a comparable software -- I mention this only for its intuitive navigation design).
2) I could not find an easy way to create items on the fly without having to add these items in a *project* window. Perhaps I didn't read the instruction manual enough, but creating a simple list, and then reorganizing it later, seems to be a better work flow for the mind, rather than having to assign all its attributes as you enter each item. Besides, not all items are a project -- some are simply Next Actions, so this is a slight digression from Allen's GTD philosophy.
3) There was no way to change the extremly small font size of the GUI. I had to squint to see what each window said.
4) finally, the kiss of death: it crashed twice in 30 minutes. As much as I would have liked to use this app, I'm not willing to invest time in an application that isn't stable on my OS 10.4.5
Nevertheless, I'll be looking for updates to this software in the future -- there is great potential with this application!