>...what are the advantages of switching from DX to FX?... > Are the advantages worth the price...
You've posted this in the D700 forum and will surely get responses explaining why it's worth the price to move to FX by people who have done so and are happy with their choice (or even, just justifying it).
I'm an amateur hobbyist, perhaps not as serious as many Nikonians, but I see the advantages of DX (for me) outweighing the disadvantages. The advantages are, you have a smaller, lighter, and less expensive set of cameras and lenses. How much weight do you really want to carry around to take photos?
I'll concede some advantages in image quality, but when I look at the quality of my own photos I'm delighted with them. So, look at your photos. Where are the shortcomings in them that might be enhanced by going to FX? If you don't see many, maybe DX is the better option for you.
I wouldn't argue this is true for everybody and that there's no point in going to FX, but I think it's true for me, and probably a lot of people who have gone to FX, just because they think its better, even if you can't see that in their photos.