Though I am not familiar with the DVD, I would think that the comments are related to "fat burning zone" or "fat burning zone myth". You can google both and decide for yourself. As with diet, there is no best exercise that fits all. Unless your body needs are very specific (traumas, illnesses), or you are training for a competition, choose the program you enjoy and can follow, and just do it.
The first thing you lose on a diet is your sense of humor. ~ Author Unknown
It doesn’t matter what diet you follow… What matters is what makes you follow your diet. ~ Tom Venuto