I've read the book and seen the DVD twice in group therapy. The first time I saw the movie, I thought "this is great!" I think having a positive attitude definitely tends to attract positive people, so it made some sense. The second time, it felt like I was being given a sales pitch or something, and it really turned me off.
I did like the idea of having a gratitude stone or something similar to remind yourself to be grateful for the positive things in your life. Its a good way to lift your spirits when you're feeling depressed.