I did my first NaNoWriMo in 2008 and wrote the first draft of my Fowlis Westerby novel (now awaiting yet more edits). I dropped out in 2009 after being made redundant a week into November, and found that job hunting became more important than a novel about aristocratic zombies. Last year, I managed to complete the first draft of a superhero noir tale set in my Vertigo City universe.
However, I am not doing NaNoWriMo this year. I think it's a wonderful way to get people writing, and the camaraderie is certainly a good boost to get that novel finished. Sadly I've got too much on my plate right now. I'm just starting a PhD in Film Studies, I will have hopefully begun the sequel to my pulp Western, The Guns of Retribution, I'm hoping to have a job by then, and I've got lots of blogging to do for my paranormal interests. Quite simply, I just don't think I'll have the time to fit in an extra 1167 words every day.
That said, I wish everyone who decides to take part all the very best of luck, and I shall be cheering you on from the sidelines!