I have participated in Nanowrimo twice so far. And I will definitely not do it again.
Here are a few reason why:
1) It usually occur at a time when I’m into editing a project and should really NOT start another book (that’s why I still have 3 more manuscripts to edit after I finish the one I’m working on – 2 of those are Nanowrimo books)
2) It distracts me from what I don’t want to do. Starting a new novel is really fun. The excitement gathered by all the other writers doing it is really fun. There is nothing wrong with fun but for me, it translates into jumping onto the new exciting idea and not ever seeing completion of anything.
3) The social aspect of it is, as I said in 2, a lot of fun. So much fun that I end up talking about the Nanowrimo, adding friends on my Nano profile, reading all the blogs about it, joining all the special email loops, and so on. All that leaves me with very little time to actually write.
4) I’m doing the writing habit thing (challenge 2 – week 1 successfully completed) to teach me to write/edit slow and steady until polished completion and submission. To see how many books a year I can produce (if it’s only one – fine, so be it! ) and keep the pace all year. Short burst like Nanowrimo are terrible for me because I think I have more time than I really do have when I chose to do it all in a short time.
5) and then we get to quality. Now this is very personal. Some people can produce high quality work by writing 10,000 words a day. I am not one of those people. I can produce about 2,000 words a day at my best, by writing two scenes a day, separated by big chunk of time where I basically write in my head while doing household chores, riding the bus, exercising, or falling asleep at night. I need to live in the book and 7 weeks in the minimum amount of time I can realistically write a decent first draft of a 85,000 words novel.