Now that was an interesting exercise.
I downloaded your iso 800 RAW file and opened it with Sony Image Data Converter. I edited it in a couple of different ways and see some very different results. I'm no expert but here's what I think...
I have to say from the outset that I think your problems stem in the main part from the fact that the original is underexposed. If you look at the histogram it is a long way from the right hand side. I think this is because before the crop there is quite a lot of light coloured wall and wood surrounding the black camera. This doesn't help as DRO will try to pull detail out of the dark areas, that means extra amplification and therefore noise.
Here's the results of my playing with the image.
First, your own image (as above) created with ACR. I hope you don't mind me doing a direct comparison in the interest of science?:shrug:
Original ACR image
Next up: Opened in IDC, exported unedited to CS3, cropped to a similar size as your original and saved as JPEG 800px wide. No PP at all.
Next up: Opened in IDC, EV+0.3, Auto noise, Auto DRO, +10 sharpening. Exported to CS3, cropped, saved as JPEG 800px wide. PP'd only in IDC.
Finally, based on my usual workflow: Opened in IDC, EV+0.3. Exported to to CS3, Levels tweaked to histogram, contrast boosted 15% and neat imaged 15% Lum, 45% Chrom, 95% Sharpening
When pixel peeping at 100% in all three of the images produced with IDC you can see every speck of the speckle effect on the top and in last two especially you can see every pore of the rubber grip.
No wonder the Sony FanBoys are in uproar about the image quality in some of the magazines comparative tests.