I've heard that point of view a lot, but it's definitely not me. In fact, if I had to pick one word to describe it, it'd probably be "liberating". I don't have to hold anything in my brain anymore, so when I'm relaxing, I can relax 100%. Don't have to worry about forgetting anything, because I know it's all in there. And when I'm ready to 'get something done', as it were, some things to do are right there. I love it. That said, it did take a while to get set up and used to.
That may be why. Lots of people don't have a GTD system. I, personally, can't see myself ever using one.
Maybe I'm just way too low in conscientiousness but I find systems like that so oppressive that I get very unhappy and abandon them.