It makes sharpening basically impossible and even selective blurring doesn't really get rid of it.
To a certain extent, the D200 has this too, starting from raw. You won't get rid of it by blurring or noise reduction since you'll get infamous blobs. Try this: in the raw developer, the "shadows" are set by default to 5%, at least in mine. What happens is that the left side of the histogram is cut off, making all near-blacks totally black. Slide that to 0% and don't do any autolevel or autocontrast in PS since it gives the same. There are better ways to enhance vibrance, like unsharp mask.
Instead of blur or noise reduction, paint over the noisy area with a slightly lighter tone, sampled from the vicinity, soft brush,
20%. The blobs and squares will disappear but original sharpness stays.
For blue skies: getting rid of the blobs is very difficult unless you gaussian blur them 30px and up, but then you will get banding. Just do that in a separate layer and mix it 30-60% with the original: blobs gone and no visible banding.
The in cam noise reduction on jpegs is pretty good and natural. Consider this: shoot raw and jpeg finest and largest resolution both. Superimpose both in PS, top layer = raw result, and selectively erase the problem areas so the jpeg layer shines thru.
