Yes, I use folders in three ways:
Within my projects, I often have one or two folders of reference information - specifically, to keep a list of project contact names, phone numbers, email addresses and their roles. This is useful for people I don't get round to adding to my phone address book.
I also set up all my Roles as folders. This is a trick to help with filtering - I can filter by Area of Life (Personal, Home, Work or Community) by using the Advanced Criterium "TopLevelParentName", but I can filter by Role buy using "TopLevelFolderName".
Finally, I tend to group projects by client name (sorry, didn't show that in my hierarchy, in my previous post to this thread) - When I create a group of projects in this way, I set it up as a folder.
As an example, if one of my Clients was Apple and I had a Project to design the next iPhone for them, the structure would be:
Work (which is a task)
_&&High Flying Designer (which is a folder - so I can find this by filtering by TopLevelFolderName
__Apple Computers (which is a folder, to keep all my projects for Apple together)
___New iPhone Design (which is a task, set up as a project in progress)
That's four levels of hierarchy. Under that would be all my tasks and subtasks for that project.
Does that make sense? Would that structure be easy for you to navigate, too, or am I over-complicating my outline?
Stéphane