Despite the fact that I use M9/M-E and M8 cameras, I’ve resisted applying noise reduction to my images for years.
I’ll take noise over loss of detail and texture any day.
On a related note, I’m happy that Leica doesn’t force in-camera noise reduction on us either.
—Peter.
Prosophos 
Completely agree, it annoyed me when I had a Fuji it only let you turn it down not off. Steve Huff also sings the prases on being able to turn it off. I have no idea why a manufacture of enthusiast and above cameras don’t let the owner chose.
Damned straight. Once the noise is gone, what’s left? Plasticky muck. The image just looks disgusting. However, I can tell you that removing chrominance noise is essential. Luminance noise, I leave alone. This applies to every digital camera I can think of.
I’ve played with M9 files and I’ve found that the highest useable ISO is higher than most people think. Most of the noise is chrominance.