Most people use Yoga for firming, toning and stress reduction. It's not really a high energy aerobics routine tho the yuppies are Americanizing it and taking it away from it's intended purpose.
There are variations of Yoga methods - a popular one now is Power Yoga which combines 2 traditional methods. I like it because it does build strength and flexibility but you should treat it as part of a well rounded program of cardio (fat burning), weight/strength training (to build muscle) and use things like Yoga and Pilates for toning.
I have a video - Yoga for Weight Loss by Suzanne Deason, don't know if that's what you bought. I liked it because they do show the variations on the moves from beginner to expert. Start slow, learn the moves and keep up with it.
Not sure if I answered your question - were you looking for feedback on a particular yoga tape or were you really asking if you can use yoga to successfully lose weight...
Every year, some people succeed. Tell yourself that in 2015, you will be one of them. ---- Started the Gym 12/16/2014