Besides the run-the-detail-sliders-down-to-zero version, RAW Therapee has three other ways to reduce noise. The one I find most interesting is the third one down on the details tab. It has two sliders to control how much luminous and chromatic noise is removed .
It also has a third slider labeled gamma. That is actually a gradient filter. It cuts down the noise reduction--and loss of detail--in the bright areas of the image where it is not needed much, but it still applies strong noise reduction to the dark areas where it is really needed.
A very neat effect. Off and on screen shots below. Notice how it balances the noise from the black background with almost no loss of detail in Laura's hair
Who is Laura and why is she being revisited? A Young Shakespeare Player who I blogged about earlier. See fun-with-imagej, November 2009