I don't like negative clarity. To me it doesn't look painterly, it just looks blech. There are other ways to get that painterly effect or a diffuse glow. Somebody posted some "painting-like" images here a while back, I don't remember the name of the plugin he used but the result was much better than what you can get with negative clarity.
I do agree that in this particularly image, smoothing out the background is desirable, though.