[Bob Nahasapeemapetilon]

I ended up purchasing NovaMind and Merlin.
I do have OmniGraffle Pro and love it, but Nova Mind is more robust for Mind Mapping and integrates beautifully with Merlin 2. They used to have some video tutorials, but it seems they are currently being updated.
Within the mind mapping application you are able to define tasks, assign start/finish dates, show percentage complete, etc.
A 'parent' activity set gets automatically updated based on the status of its subtasks.
And Merlin can also import OMNI Outliner documents. I have not tried that feature yet, though.