Nikon D5000 High ISO RAW Image Quality
We've recently started looking at RAW files converted with dcraw, an excellent freeware raw converter. dcraw usually offers timely support for the latest cameras, but more importantly, it does not apply any noise-reduction, sharpening or other corrections such as geometric distortion correction to the output files. (We found that Adobe Camera Raw still applies some limited noise-reduction when its NR settings are set to zero, and it also applies other corrections depending on the make and model of the camera). There will always be differences between RAW converters, in terms of the sort of de-mosaicing algorithms they use (the processes by which they convert the separate Red, Green, and Blue data sets to an array of full-color RGB pixels), but dcraw seems to use a fairly generic algorithm that delivers good sharpness with relatively few artifacts, and can be counted on to not apply any noise reduction if you don't want it to.
Below are crops from Nikon D5000 high ISO RAW files compared to RAW files from the D60 and D90, converted with dcraw.
As was the case with the JPEG results, there is virtually no difference in converted RAW files between the Nikon D5000 and Nikon D90. Both the D5000 and D90 handily beat the Nikon D60, despite the D60's lower resolution of 10-megapixels.