There is some disagreement over on this Wikipedia discussion page:
It discusses the main Wikipedia GTD page pointing to this page - a list of GTD software but heavily populated with adverts for their non-gtd coaching and methodology:
...Which links to this page explaining why their methodology is better than GTD.
So if you have an opinion (either way) about this, I'd encourage you to weigh in. I have a potential bias as I develop GTD software but I feel the issue is greater than that. Surely a page that is linked to from the Wikipedia, about GTD, should point to someone (anyone!) who isn't promoting their own alternative methodology?