Any reason not to contract the car before taking delivery

[bracoX5d]

Hi All,

I'd like to introduce my self, this is my first post although I've been reading the posts here for a while. I have found this site to be a great source of information, and it has kept me busy while waiting for my X5.

So I currently have on order 2010 X5 35d, Space Gray, Tobocco leather, premium package, technology package, rear climate package, and I am very excited to take delivery. However, there is a chance that I won't take delivery before new years, but I really want to take advantage of tax benefits on my 2009 taxes instead of 2010, my dealer says we can contract the car before I take delivery since we already have a VIN#. Is there any reason not to do this? Any pitfalls I should watch out for? Hopefully I won't have to do this as my car is on its way to Oxnard VPC, but I'd like to get some advice if I do have to.