I really don't care what the reviews say, my DS has less noise at high ISO than my friends D70 and I certainly do care about image quality and my DS does not soften the image more than his D70.
Also his D70 consistently blows out the highlights, where my DS does not. He is a professional photographer committed to Nikon, but is still constatly amazed by the quality of the DS images.
Possibly you should get a DS and a D70 and do your own comparison like I did. His D200 although a great camera, is noisier than both the D70 and the DS, as you stated.
What I can tell from my 2 year+ *practical experience* with my *ist D and DS is noise at ISO 1600 is too high to be acceptable and underexposure will get thing even worse. I was forced to NeatImage the pics if I want to get rid of the noise - but altogether with some degraduation/loss of object textures.
At 800, it is okay but then pls don't look at the shadow areas..
With my K100D, I bet you'll probably face the overblown highlight problem you mentioned, but it will worth for the tradeoff because more levels will be recorded especially for the shadows. But then afterall, pls remember the photographer can choose *where* to meter as long as the light meter of the DSLR is accurate. Unfortunately, I don't think neither the *ist DS or the D of mine are/were accurate, except the "fool-proof" Pattern/Matrix mode - but don't forget these are not controllable and predictable then. If you want to control where to keep highlights or shadows totally, never use the Pattern mode! (but again, provided that the camera's metering system is acceptably accurate at the first place!)