Isabelle Huppert is a wonderful actor. The director of "La Pianiste" understands this, providing the viewer with long takes of Huppert's face, and these are a pleasure to see. Huppert is not an animated actor--she registers emotion with the smallest lift of an eyebrow or flicker of a smile.
Other than the enjoyment of watching an experienced actor excel in her profession, there is nothing in this movie that makes me want to recommend it. (Well, if you enjoy self-mutilation, sado-masochism, and bizarre behavior, "La Pianiste" might work for you. Other than these attributes, I could not find any redeeming value in it.)
Buried in all this strange material there is a kernel of truth. People who compete at the very highest level--musically, athletically, whatever--begin as strange people, and are shaped into stranger people by the competitive environment.
Not worth a trip to a movie theater to relearn this life lesson.