I wish I had taken this sort of time for the past two years of NaNo, but I also know for a fact that I couldn't motivate myself to sit there and write background story and outline. This group is absolutely brilliant because with so many other people there motivating you to keep going, you forget that the laundry hasn't been done yet - and the result is a Novel that is exploding to get written.
I want to disagree with the previous reviewer on the interview challenges. I feel they gave me a chance to play with how my characters interacted with people other than each other.
My favorite challenges were definitely writing the background stories for my characters. I'll be able to give desire and motivation to characters I might otherwise neglect.
I've enjoyed looking back on this last day and remembering what my novel was before starting the prep challenge, and I can see a huge difference between then and now. Giant really. I feel like 50,000 words will be no problem.

...but we will see! 9 more hours where I'm at!!!