I too have tried Process, although I didn't buy a licence in the end. As Steve says, it's trying to be a task manager, rather than an outliner, although it could be used as such. It appears to be unusual in that regard; I seem to remember it calls itself an outliner -- almost as if you're meant to use it for outlining a project before exporting your plan to a recognised project manager.

I was searching for a simple project manager, something between OmniFocus or TaskPaper and OmniPlan or Merlin. (A not-dissimilar application that was mentioned recently on the Scrivener forum is Hot Plan by Intuiware.) I came to the conclusion Process wasn't what I wanted, partly because its development rate seemed rather slow.