I doubt that someone would be taking better pictures just because they're moving from a D200 to a D700 :P
couldn't say it better monty
buying a new camera will not make You a better photographer
oasisfan33 - for me the answer to Your question is simple. If You are using (or You know that You will be) high iso, than Yes go for d700, as You can't find a better deal (d3s is too pricey for now). If You wanna switch to d700 only to use lower iso, than I would wait for some time, as You wouldn't see too much improvement in IQ. Sure d700 has bigger viefinder and some other tweaks, but the question is: will this affect Your way of taking pictures? will having live view make You a better photographer? is dust cleaning worth spending $2.5k? for me the answer is no. But it's up to You only.
I have d200 and was having the same dilemma last year, I had even the d700 at the cash register once. I'm glad I haven't got it and spend the money on glass - as this really boosted my pictures.