You have been wondering how does D300's ISO6400 performs? Wait no more, here it is! Below a photo taken with Nikon D300 with 17-55mm F2.8 lens.

Actual photo with exif in Nikon Capture Original photo resolution: 4288*2848

A quick look at the exif:
[Image]
Make = NIKON CORPORATION
Model = NIKON D300
Orientation = top/left
Software = Ver.0.25
Date Time = 2007-08-30 17:59:32
[Camera]
Exposure Time = 1/320"
F Number = F2.8
Exposure Program = Aperture priority


 

The focused area

Image above is 100% cropped of the photo's focus area. Details seems to be slightly washed out and wordings are not as sharp. This may be due to handshake but a further processing should solve this issue easily.

Image after post processing

The same image but USM and processed with Noise Ninja in Photoshop CS3. Wordings are clearer now. At ISO6400, this amount of noise is acceptable and until I get to hands on a D300, I would say that it is fairly usable.