Something I believe: let your output dictate your systems.
If you seem to manage everything just fine, don't adopt GTD.
If you currently produce high quality output at a rate you're satisfied with, don't adopt a better note taking system.
Upgrade only when something breaks.
Conversation
(In a couple of months, if I turn out to be a total ‘second brain’ acolyte, the right question to ask is “what broke?”)