The DeNoiser basically does what we normally do in Photoshop which is like put a slightly soft effect on an image and gets rid of a lot of noise. You do lose a bit of fine detail but some of it comes back the longer you let it run.
The initial value is at 8, so DeNoiser starts after 8 iterations. I'd change that to 100-200 or so to get a fair bit of the fine details rendered and then use DeNoiser to finish off a stubborn image. There's a slight lose in fine details which I think is fine for animations, wide shots, architecture, environment, etc. Might not be super ideal for like a close up of the face.
IMPORTANT NOTE. Don't overwrite your 4.10 studio. The 4.11 is a beta and has issues like weird thigh distortions when applying bending poses and a few other things. I'm sure a patch will come out. But still, for a first go the DeNoiser should be really exciting for those with older machines or who do lots of animations.