I've done National Novel Writing Month -- an online challenge for participants to write an entire 200 page novel during the month of November -- for the last couple of years, and I plan on doing it again this year. I really love it. I love knocking out those pages and typing my daily wordcount into the website's graphing thing, etc. (Take a look at the website: it's really neato).
However, I'm not sure how useful it is to a person, such as myself, who takes writing perhaps a little too seriously and wants to do it well. In order to produce that many pages in a month, most of us have to wrestle our internal critic aside and just write anything. That can be a great relief and lots of fun for a person, such as myself, who has a bully for an internal critic, but how useful is it? Can it produce work worth reading? I'm not so sure. My first NaNoWriMo novel was pretty unintelligible; maybe one paragraph out of the 200 pages was something I'd want to keep (it described a character's losing an eye, haha). The second one had more decent stuff in it, but it, too, was as close to being a real novel as my latest grocery list.
It makes me question the whole idea of the "shitty first draft," the creative writing idea (Anne Lamott's, I think) that just getting words down on paper, any old words, is better than nothing, because then, at least, you have something to revise. But the work involved in polishing this "shit" is often much more overwhelming than writing a thoughtful draft in the first place.
Ugh -- but then again. It's true that you can come up with marvelous, inspired stuff if you're just counting pages and aren't too fixated on its being marvelous and inspired. And is it not true that my last NaNoNovel is the only thing I've come even close to finishing in a very long time?
Anyway, whether or not NaNoWriMo produces anything worthwhile is beside the point. Isn't it? If one takes writing too seriously, it's probably not for one.