I go to a Kundalini yoga class. I enjoy it a lot. I find it is good for stretching, strength and relaxation. It usually isn't aerobic although sometimes we do sessions that are somewhat aerobic. It just depends. It seems like all the different kinds of yoga use the same poses, but some don't focus as much on the breathing and meditation and that's really an integral part of yoga.
I have a very good tape of Kundalini Yoga with Gurmukh and it is produced by Living Arts. I do feel like I've had a workout when I'm done. I also have two tapes by Rodney Yee from Living Yoga also from Living Arts. One is abs and the other is power yoga for beginners. His style is different from what I am used to, but still good.
For weight loss, you may want to supplement yoga with something else, walking, or something. I do an eliptical trainer and swim. There is also something called Breathwalking, where you use yogic breathing patterns along with walking and so you get the benefits of aerobics and yoga. I used to do that a lot but I havn't been walking much lately because of foot and knee problems.
Also, if you are a stress eater, yoga can help relax you and give you better self-control and benefit your weight loss in that way.
Good luck! Hope I wasn't too long-winded. I really enjoy yoga so I had a lot to say about.