I just came across this Ximagic Denoiser plugin (currently Windows only; MAC version is planned):
http://www.ximagic.com/d_screenshot.html
This Denoiser is definitely something for people with time for some fiddling with 7 different denoising algorithms. I will need some time to test it. The examples on the webpage look very good however - and it is freeware.
The author also offers similarly comprehensive freeware Dithering and Quantization plugins.
