Good Post Bobby.
I use Toodledo and find it well suited for GTD expecially considering its tags, contexts, and locations. It doesnt do the folders well and its interface can be a bit clunky.
I am trying producteev for its subtasks and workspace sharing. Your post us helpful and while I use labels for context, I am trying your approach of multiple workspaces for folders… How do you get them to appear across the top like that? Mine appear in a big box with large pictures along the top and everytime I change I have to drop down. Did you modify the interface?