I came to know about Ttapp one year before I came across Cathe. They are two different approaches to fitness. Ttapp is not easy to master but once you get it you will find tremendous benefits out of it. It took me really a while just to master the Beginner/Rehab portion. However, I would say that if you try it and don't get the form right, you won't appreciate the benefits. Having tried Ttapp I would say they are very beneficial to your body. It is not really about weight loss but has an impact on lympathic aspect in your body. Don't really know how to explain it but if you go to their website, there are more writeups there or if you join their forums, you will learn a lot more.
In my case, I have to say it helps me tremendously in addressing my knee joint pain problem when I first started. It also help in back problem too. The exercises do not have the fun factor as other form of exercises but like I mentioned before, once you understand the logic behind it and you have tried it successfully, you would appreciate it. There are some signature movements there that are fantastic such as Hoe Downs, half frogs and their signature back stretch.
You can go to their website to try out some of the free exercises. I did that and that is how I came to own many of their dvds. Strangely, Ttapp compliments CAthe's as one stretches the muscles and one work the muscles but both tone the muscles up too. Ttapp is like weight training and yoga put together.
Hope it answer your question.
Shelly