I have owned a D100 and now a D200. In fact I was so impressed I bought two D200 bodies for walking around.
I used custom curves and messed with the color of the D100 a lot and finally got it where I wanted it. I bought these two cameras, and leave them on Automatic WB most of the time and have yet to be disappointed in the results.
I would be interested if you find a good custom curve, as I may try it just to see if it improves anything, but so far I have yet to come up with a complaint on these two fine pieces of equipment.
I can't complain about the D200 either. I've had it for a couple of weeks now. I use it mounted in a copy stand for macro work, my colors are so critical that I use a grey card with the preset WB. I'm very happy with the image quality I get with the D200.
For a walkaround I use the D50. I like it because it's a lot simpler to use in the field and weighs considerably less than the D200.