That's a lot of words being pumped out each year. While there are naysayers, there is little bad to say about an activity that gets people out of their mundane lives, off their asses and writing something. I don't believe that a finished first draft HAS to be a masterpiece for Nano to be worthwhile.
I learn a lot each time I sit down to do Nano or SoCNoC. The biggest point is that writing requires one to sit down and write. You have to put in the hours or nothing will get done. It is that simple, yet many, many young writers believe it is otherwise. A round of Nanowrimo will get you over that mindset and get you putting in the hours writing.
I know it's been said before. I know it will be said again, but that is the only bit of noveling that absolutely must be said. Everything else happens after that step, so it is absolutely required first and foremost for anything else (like finishing a publishable first draft, to getting it published and getting it read and critiqued and on the New York Times bestseller list etc...).