I too use Topaz Denoise, it works quite well. (Better than CS5 IMHO)

One trick is to use a very light setting as the very first step in your workflow and then use a heavier setting at the end, maybe just on the background or areas with no detail.

Another idea....You can also considering running a Gaussian blur or Surface Blur on a very light setting prior to noise reduction....this can really smooth things out nicely.