Sign-ups will close at 11:59 PM Eastern Time on Saturday, January 2, 2015, which gives you all a full six days to join, and enjoy your New Years holiday. The first challenge will be held on Sunday, January 3, 2015!
This season's twist is really clever and does exactly what a twist should do; that is, it adds a completely new aspect to the game without taking away from its essence. I would have never thought of something like that, and I'm very excited to see how it plays out.