I'd like to see some way to generically group projects as well. I'd like to be able to OPTIONALLY assign an area of focus to each project, and be able to view all projects grouped by area of focus (at monthly review time but not day-to-day).

I remember when I first started GTD I didn't "get" the different levels of focus but now I appreciate how it fits together in a very loose hierarchy. I had a minor epiphany when I realized some of the items on my project list were actually not projects but ongoing areas of focus which would regularly spawn projects.

I don't see a lot of value in going above the "areas of focus" view in a software program though.. I think actions, projects, and groupings of projects are enough. For instance, some of my areas of focus actually satisfy more than one of my personal goals so everything tends to get fuzzy past the 20,000ft view. Besides, I don't have 500 life goals that I have to slice and dice and sort, like I do projects.

It's interesting, outliners like OmniOutliner are a little too top-down, you can add children to items but you can't easily switch the parent. For GTD, it's nice to start at the leaves and work your way up, so I can't wait to see how the two approaches might mesh in OmniFocus.