I have nothing but respect for those writers participating in NaNoWriMo, and I hope everyone will be successful. I've never participated, and honestly I can't imagine writing 50k in one month. Especially in November when there's sweeps television on!
Maybe if I didn't work full time as a copywriter I'd be more inclined to participate, but the idea of writing all day at work and then coming home to hours more on the computer to crank out those 50,000 words just seems far too daunting.
Personally, I find January to be the best month for holing up with my laptop. Perhaps I'll do JaNoWriMo in 2010, but with a more modest word-count target. Might be a good way to beat those post-holiday January blahs.