I'm doing it (a historical mystery, my favorite!). I've had this idea in my head, percolating for a year, and finally figured out what to do with it a little over a month ago, so I decided to try the Nano thing and see if it works.
I've gotten my 1,667 words down for today already. Anything else will be just gravy for my Monday, seeing as how I've got a mess of dishes to do, and still quite a few rewrites for my main WIP that I need to finish before I begin submitting it to any more agents.
I went to our Nano kickoff party here the other night. It was fun, but I got seated next to an obnoxious 14 year old, and it seems as though I and one other guy are the only extroverts in our "cabin." It took forever for everyone else to loosen up. I'm hoping we can socialize more with the other folks at future events.