I recently went through my entire OmniOutliner Pro notebooks and added every outline into the notes section of a task within each project outline in OmniFocus. Now all of my project management data, and all of my tasks are all located in one place.
No more switching back and forth between multiple programs. Some outlines were so large that I broke them down into multiple note fields. This allows them to be opened and closed individually as needed. When I am just working on tasks I close the note fields and they are conveniently stored out of the way. Perhaps one day OmniFocus will have the ability to outline within the notes field. This would be especially useful if the fold function were available. I did have some issues with text formating that took a while to straighten out, but it was worth it. Would be nice to have more formatting control of text in the notes section. There may be more to formating notes that I just have not figured out yet.
There are still some issues to deal with using this method. Like some of the other users, I set up a new context named "Project Notes", and each task that is actually just a place holder for a project note is written in caps. Usually something like "MDI PRESTON COTTAGE PROJECT NOTES:" This easily differentiates them from normal tasks as you review your to do lists.
I personally like having all of this data synched to my phone, but if you don't you can simply remove the Projects Notes context from synchronization with iCal. I am synching with a blackberry, and have not noticed a significant increase in synch time.
Now if I am out in the field I can easily search my tasks for the project name and view my entire project notes as well.