I think it’s a good learning exercise to build a GTD tool with Tinderbox. I used mine for a while, but ultimately prefer OmniFocus for task management (mainly because it has awesome auto-complete, archived stuff disappears from auto-complete, it’s a lot faster than agents updating… well, lots of reasons 
)
BUT!
OmniFocus does not do a good job at providing The Big Picture – that’s where Tinderbox can really excel. You may or may not need to link from Tinderbox to OmniFocus. If you do feel you need to, it’s easy.
Try it out and see what you think though… what works for me may not work for you.