I once received an email from David Allen at 4-something in the morning. Seemed to me a strange time to send email, but it made me think that this GTD thing is not the real secret.
The real secret is motivation. GTD is just a really good system. It takes alot of gumption to make it work and a strong, definite purpose that drives the behaviors necessary to make GTD work. I suspect that many of us who spend alot of time tweaking our system dont need a better system - we need more gumption and clearer purpose. The former (gumption) probably follows the latter (purpose).
If you arent out to move mountains, you dont need a very good shovel, but for some strange reason you feel like you're accomplishing something by hunting for one.
I've found that my purpose for using GTD is primarily to keep stuff out of my face. Thats not a strong enough purpose to drive GTD behavior.