I also ordered the 18th and I am still processing! I mean really? They didn't know this was going to take off with Christmas expectations?
The "still processing" is not written in stone. Your order is probably on it's way. When I placed my order this morning, I noticed one of my orders several orders back is "still processing". A couple orders after that one, the status was listed as complete. All of my orders have been delivered and not delayed. You may be surprised and receive it today or tomorrow. At least, this is my personal experience.
I'm sure SI is working feverously to get all orders out in a timely fashion.