NaNoWriMo is an interesting experience. Oddly, it's a different interesting experience every year.
The first few years I did NaNo (starting in 2004) I was just excited to be writing. I wrote and wrote, and at the end of the first year I had an incomplete mess. I was happy with it, because I won. I wrote 50,000 words that year, finishing at about 11:50 on November 30th. But during the process I realized I had to write straight through--I couldn't skip to the end, or write that interesting scene floating around in my head.
At that point I had about a dozen unfinished novels floating around--plus 1000 or more bits and pieces less than fifteen pages long--and most of them had incomplete middles. I wrote the beginning, and when I got bored with it I wrote the ending. I never got around to writing the incomplete middles, I was too busy working on the next project.
At the end of the second year I had 50,000 words. I'd written straight through, with a few exceptions. I had a beginning, a middle and an end. It was still a mess, but at least it was an organized mess.
I never edited either of those novels.
The third year I had a complete novel, and one I couldn't stand. 2007 was the first coherent novel I got out of NaNoWriMo, and I liked it so much I shipped it right off to my writing group, convinced it was perfect.
Oops. That one's still not finished, but at least it's in editing.
Each year since then I've participated, and each year it gets better. In 2008 I wrote Beauty Syndrome (which turned into two books) and in 2009 I wrote DemonBorn. DemonBorn was my first introduction to the Ameso in my fantasy world. I made a serious mistake (from one point of view) and decided to write the sequel in December. It was actually finished in February of the following year, but it was finished. I now have three (and a half) books in that series.
It continued like that. Last year I wrote The Monster at the Heart of the Castle, which is finished and ready except for final edits.
This year I broke from the pattern and wrote a futuristic dystopia for adults. I'm almost finished.
NaNoWriMo is one of those things that you either love or hate. I love it, partially because it taught me to write--not the dialogue and the sentence structure and passive verbs, but just to write. To make writing a priority and write every day.
I had someone tell me once, "You're writing like a professional!" and that's what I hope to be someday.
We'll see, but without NaNoWriMo I wouldn't even be close.