I am using the current version of ACR, both in LR4.1 and Photoshop CS6. Recently shooting with a Canon 5DIII at relatively high ISO (6400, 12800) I have been fairly successful using the luminance and color noise reduction and sharpening to get rid of the noise. I am pretty good at balancing the detail, contrast and amount sliders to retain detail, and I followed Jeff Schewe's advice on adding a tad of grain to finish things off.
However, I tried careful adjustments of noise and detail in Topaz Denoise 5, following the advice in their video tutorial that says to zero all of the ACR controls, not just of sharpening and noise reduction, but of all other controls. After working on several images of different degrees of detail and high frequency, I found that I have been consistently able to get better noise reduction with more detail brought back using Denoise 5.
The problem, of course, is that this costs me many of the advantages of shooting RAW, in that I give up some of the really powerful tools in ACR, such as highlight recovery, use of color balancing before converting from RAW, the use of the great Clarity slider, etc.
Topaz' staff feels that zeroing all of the ACR controls presents Denoise with accurate representations of the camera's noise parameters at a given ISO, and it really seems to work that way.
Has anybody here considered this issue? Have you processed a file in ACR and then used Topaz Denoise and got really good results? My thinking is that correcting white balance would not negatively influence the nature of the noise, while adjusting the Black point to the left would possibly make noise removal in Topaz more difficult. Tomorrow I will try some tests, but would still like to get people's thoughts on this.