We all want different things with our photography, so when someone says 'why do you want more MP' or 'why do you want ISO', what they're really saying is 'i dont need more X for what I do', and thats a totally valid thought to have.
I have a D2x, and it could probably serve me fine for many more years. I'll probably just wait and see what the fabled magical D700x will be like when it arrives. But I have seen the limits of my D2x in practice, and I know ive missed shots because of it. Maybe im a bit of a perfectionist, but it's the way it is. The D2x is just a bad performer in low(er) light situations. No amount of arguing with that will change my opinion, because i run into it all the time in reality. You may then say 'it's the artist', but I respectfully disagree. I am not talking about the content of the image. If the image has a beautiful composition, or nice subject, or whatever.
What im talking about is being in a remote location of Indonesia, it's late afternoon, you're in a beautiful cave with overhanging foliage, and your mind is racing and seeing all kinds of interesting angles and shots. Until your camera says.. 'sorry dude, i need to be in ISO1600 to get that', and you go 'ARGH!', never mind then because it'll be crap. You still take the image, but what you already knew is painfully obvious when you look at it later. Then you check out your friend's D3 images, who was sitting right next to you, and has the exact same shot, at ISO1600, and it doesnt look like its snowing. It's actually usable. And unfortunately you cant go back with more daylight because the boat is already moving to the next location.
Sure, maybe I should have never gone into that area, knowing the limits of my camera, but thats exactly what this is about for me. I feel the camera should not limit what I want to achieve. Its a tool, nothing more. If science creates a better tool, where the limits have been stretched, i think it's crazy not to explore that. (but not quite $8000 crazy).