GTD annoys me. Following GTD seems like a recipe for writing a bad song. Clearing inboxes, putting things into buff coloured manilla folders... focussing on the 'next step' of projects... What is the 'next step' in writing a song anyway? Mostly it's going to be sitting down and pulling your hair out! There is no tidy way! I am going to have 50 tabs open on my computer when I write. I'm going to be reading 16 books/articles/blog posts at the same time and none of them may contribute anything.
Covey is simple. Spend most of your time on quadrant 2 stuff. That is all.