If you have the cash and want to spend it, it should be an outstanding camera. If you haven't pre-ordered, it could be tough to get one before January. I'd order now. B&H Photo, Adorama and Amazon are great, trustworthy places. Ritz is good too, but can sometimes be pricey.
If you want to save a few $$$, the 300 is not a huge advancement over the 200. It does have some interesting features like live view, but as picture taking goes, there doesn't seem to be anything revolutionary in the 300. The D3x is a huge leap, but it's almost $4k!