Just checked this out and I must say I am impressed with the result⌠though its slower than old denoise.
A few spontaneous thoughts from a user: 1. I miss a slider for adjusting chroma denoise. 2. Do not remove the old presets please, they were introduced just 1 year ago I think. Old denoise is faster and useful when noise is not so strong. And some users like what they are used to. Though I admit it is somehow misleading.
Iâm not using darktable, but how is the new noise reduction compared to RawTherapee ?
In terms of quality/result similar, maybe a little bit better. In terms of speed, worse. But the math behind it seems to be different, and so the usage is different, too. I donât know. I still think RT is better in terms of sharpening/demoisaicing/noisereduction/resolution, but dt has other advantages. New denoise in dt is certainly much better than old denoise, especially with high iso shots. Overall new denoise is simlar to RT. If you want to use new denoise you should have GPU acceleration (OpenCL), otherwise it must be really slow.
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Ok, thanks. Iâm using RawTherapee a lot, but if I encounter a high iso noisy image , I skip RT and do all my edit in DxO.
PRIME Noise reduction is also slow/very slow. 
You can use the central pixel weight and the force sliders to get an effect similar to what a chroma slider would do
There is no plan yet to remove them (although they have been adjusted a bit to prevent highlight clipping) 
Chroma noise doesnât exist. Itâs just noise that doesnât affect the 3 RGB channels at the same time.
Great work on the noise reduction 
I find the âpreserve shadowsâ slider very useful. In darktable 2.6 I sometimes used a parametric mask to increase the denoise intensity in darker areas, the new features make that much easier.
This is a photo without denoise:
This is with the default settings in profiled denoise:
And finally with a lower value for shadows preservation:
In my experiences with the new profiled denoise the loss of detail is very low, the darker parts become a bit darker than before and you lose a bit of sharpness in the image. But you can easily compensate that.
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nice work @rawfiner!
I have found that you get excellent results when you combine your new profiled denoiser with a contrast equalizer:
ISO 640
denoiser alone (standard setting):
with contrast equalizer applied afterwards:
ISO 1600
denoiser alone:
with contrast equalizer applied afterwards:
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Does new denoise support GPU acceleration?
Yes it does 
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18,598568 [dev_pixelpipe] took 0,027 secs (0,046 CPU) processed `denoise (profiled)â on GPU, blended on GPU [full]
Yes
Ok. Yes, thatâs in about the same as I âmeasuredâ - I counted 3 secs wit GPU and 5 secs with CPU. LOL
Are there changes to the camera profiling to determine this parameter? If yes, do you recommend that we re-profile cameras to get best results?
No, camera profiling has not changed yet. The work to change it is started, but it is quite hard to make the fitting accurate enough, and as denoising with the parameters infered by the heuristic with old profiles works quite well, I donât know if it is worth it to continue it. I think I will rather spend some time to try to create a blind denoising module, that would not need any profile but would adapt denoising to the noise characteristics of the image nonetheless.
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I have made a video tutorial to explain how I use the module and all its sliders:
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I have a question concerning new denoise profiled non-local means: does this method work in (linear) RGB? I think old denoise (presets/wawelet) worked in Lab, didnât it?
Yes, the inputs are in linear RGB. The old presets worked in RGB too, but used âcolorâ and âlightnessâ blending modes
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Great, thanks for the quick reply. So old denoise, was RGB, but not linear RGB?
It was linear RGB too. Denoise profiled position in the pipeline has not changed, so the inputs are exactly the same as previously
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