Oh, it seems to be different from last time. Its not first come first serve (which crashed amazon). You vote for the one you want, and then on the day of there is sort of a random drawing to see if you get the option of buying.
Even if your choice doesn win the poll, there is still a discount! Here are the runner up prices:
Wii: $199
360: $219
PS3: $319
So vote for the one you want! The Wii is pretty much guaranteed to win the poll, but if you're buying one of the others anyway you might as well try your luck. Sadly I wont be around a computer on Nov 22 (when the drawing is held).