Here's kind of an introductory article called Five Reasons to Stop Saying "Good Job"
And then here's an article where he clarifies that he doesn't mean to praise less, or to use more meaningful praise than "good job", or to praise effort rather than ability, or that the reason he doesn't like praise is because it makes kids get spoiled. He simply thinks praise is bad. http://www.alfiekohn.org/f_news/fullnews.php?fn_id=5
And then here's an interview. http://life.familyeducation.com/discipline/parenting/36516.html
The overall idea is that praise is part of behaviorism, and that behaviorism in general is manipulative and hurtful to kids. So this would include punishment, rewards, sticker charts, etc. He feels that praising kids teaches kids that they're valuable only when they're doing what we want, and that it has some bad long-term consequences (talked about in the articles.)
So, what do you think? Do you praise? Do you try not to?