Really there are two different schools of thought. Carol Dweck is the one who really popularized the research emphasizing the importance of praising work versus innate ability. This is the research that has gotten a lot of attention in the media. Alfie Kohn has a bit of a different approach. He emphasizes that the problem is external evaluation and praise takes away from a child developing their own internal motivation and self understanding. Praise can be manipulative and put children under pressure.

It sounds like the original poster's son might appreciate Alfie Kohn's position more. http://www.alfiekohn.org/parenting/gj.htm