Do not wait, open and use immediately. With tech items you are robbing yourself of useful life if you wait. Things move so fast now for devices like these--They become somewhat obsolete in a short period of time. If you spend the next couple weeks learning your N7, by Christmas you'll be ready to treat yourself to some nice paid apps (If you can afford it) or even rooting.
Having said that, I purchased the N7 for our family partly because it will have better staying power than something like Kindle Fire or a Nook. It is a family Christmas present, but we are using it right now.