I like NaNo a lot. In concept. I have done bunches of them, and usually finished. Last year, I sat down on Nov 1st and spent the next 2 weeks writing. I got about halfway through the novel, and asked myself why I was wasting time on it. It was not NaNo's fault. It was that I had the germ of an idea for a novel, and two weeks later, I had 25,000 words of utter crap.

I could have written another 25,000 words of crap to finish, but have enough respect for my own time to just decide to table it. The stuff I wrote is still on my drive. Maybe it will get another edit. More likely I will stumble across it in a few years and wonder why it hasn't already been deleted.