This is probably an overgeneralization, but I think there might be two kinds of perfectionists (or two perfectionist-like qualities in people): those who don't want to do something unless they can do it perfectly, and those who won't stop doing something, stop trying, or call it "done" until it's perfect.
Both exist in me. The first is, for me, really a fear of failure, and it sometimes keeps me from trying new things. I don't want to learn to rock-climb because I have to do it perfectly or the consequences could be disastrous. This isn't really perfectionism, though; it's a fear of failure, of looking stupid. (Intellectually I know that I can take safety precautions to avoid disastrous consequences.)
The second is, for me, something that gives me pride. I don't want to go at something halfway and then quit. I don't want my work or my life to be "good enough." I want my work, my life, my relationships, my health, to be as perfect as I can get them. And it takes trying, failing, tweaking, trying again, starting over, taking a different approach, letting something simmer while I think it over, etc.
If you're describing the first characteristic, you'll probably be frustrated when you start implementing GTD. It's a process of training your mind, of starting, fostering, and growing new habits. Plain and simple, it isn't going to be perfect at the moment you start.
But if you're describing the second characteristic, you'll enjoy implementing the GTD principles and finding out what is "perfect" for you. That might mean starting with paper and moving to a Palm, using a tickler and deciding you don't need to, or doing a weekly review and realizing you need to do it more than once a week (something I recently realized). If you're goal of a "perfect" implementation is being the most productive, efficient, calm, and ready person you can be, taking this on will be rewarding.
