What a smooth picture like that!!
These pics above were shot by Sigma DP2s in various ISO settings between 100-400, EXIFs are able to be checked. I must mention that there should be much noise in the picture(especially in ISO 400), but they was erased by the way that I don't know.
These pics looks very "smooth" but with sharp edges, especially compare to the untouched ones like "http://www.flickr.com/photos/pootaro/7533736520/in/set-72157630430289506".
I've tried several ways to perform like that, but none of below was successful.
1. Reduce Noise (or Median) + Sharpen Edges all by photoshop.
2. Imagenomic Portraiture.
3. Use Oil-painting filters.