Getting Things Done?

machinder asks: "In reading Cory Doctorow's notes for the Life Hacks presentation at the O'Reilly Emerging Technology Conference, I saw reference to David Allen's book Getting Things Done. Casting about for it a bit, I see a lot of developers have touted the thing in their blogs. I'm sold, and am starting to implement this system, but I'm wondering if any other Slashdot readers have used the system, and if they have any advice?"