I haven't read through everything yet, but I wanted to say I agree with you Richard. I have a D200 and a D5000. My main camera is a D3 so when I pick up the others it is for a specific reason. The D5000 I have never been able to get that intuitive feeling where you can just shoot. The D200 and D3 do that for me. I have shot with them enough and they are comfortable enough that I can pick them up and go.
I have been considering replacing the D5000 with a D7000 to see if it improved the situation. My D5000 is a 'travel', knock around camera that I can hand to others to snap a picture with me in it. I don't hand over my D3 at all and my D200 is pretty much just studio type work now with the a portrait lens.