After 5 classes, I can safely say that this is just not the workout regimen for me. I get an okay workout, but I just don't really like the format.
The teachers are great--especially Dana McCullough, the best ever yoga teacher over at Body Heat--and I can definitely see how it is great for some people. They provide childcare for while you are in the classes which again would be great for some people.
Also, the people who really looooove this method have to really love it financially--for 170 bucks a month I expect to be sore after every single class AND have a golden-dipped protein bar after each class. I wasn't sore after most of my five classes, so I just don't feel it's worth it.
Pro tip: Even though you can work out in bare feet, I suggest grippy socks. The floor is sometimes real slippery!