I adopted GTD back in college (around '08-'09) after learning about it from Merlin Mann and reading about it in the book "Dreaming in Code." If it taught me one thing, it taught me to learn how to say no to commitments. Sure, I'd like to work on this fun software project or go to this hackathon, but then I think of all the work it will take and the existing work I'm committed to. At that point, as much as I'd like to do otherwise, I say no to the proposed commitment. GTD is core to my life. All my commitments are consolidated and up to date in my Things app. I honestly couldn't imagine how I could have been productive without it.

edit: I also recommend those familiar to GTD to listen to Merlin Mann talk about it on his Back to Work podcast: http://5by5.tv/b2w/95

Helps you rediscover some principles about GTD.