I've never done it before. I have written 50k in a month before--on rewrites, which means I've already got the basic novel done in a draft form, making it much easier to do the massive word count in one go. I've not really timed myself before, but I don't think I've written 50k of a new draft in a month.
And I've never participated in NaNoWriMo for another reason--I've never been in a situation where November provided me with a good opportunity to start a new project (because, of course, the idea is to start--and finish--something brand new in a month). I usually draft in the summer and revise in the fall and winter, so November has been a bad month for me to participate.
This year, I find myself in the last week of October with a shiny new idea. And a need to finish a new draft. I got on Twitter and mentioned NaNoWriMo, and several friends immediately said they were participating, too.
And...well, let's just say that I can recognize the fates lining up when I see them.
So I did it. I signed up for NaNoWriMo.
Will I finish 50k of a new book by the end of November? Honestly, I don't know. On the one hand, I have a lot of travel lined up for November--I'll be gone literally half the month. On the other hand, carpe diem.
What about you? Have you ever participated in NaNoWriMo? Why/why not? Any pointers?