How big is your project?
To me, GTD project management is great, on the condition that its generally used for more self-evident projects. DA refers to some projects may need more horsepower - if they do, well then they do.
It does bring up though how big is your project. Are you planning with that takes a team of 15 a year to do? Is it as simple as a 2 or 3 step job? For 2 or 3 step type projects (which a lot are), then the natural planning model is fine. Some projects may need the full scale of planning power of a PRINCE2 or a PMBOK or a MSP. Just make sure the tool fits the job.