Ow, ow, ow . . . I did levels 1 & 2 of this (skipped the warm-up on Level 2, 'cause I was already warmed up). This is one I could see buying someday (tried it via Netflix), because I think there's a lot of room for growth here! Did I say "ouch" yet? All the holding halfway down in push-up poses . . . and now that I've tried it, I really want to get good at the crow pose.
Anyway, most of the idea here seemed to be taking the "power" yoga poses and going in and out of them for several repetitions, and then when you were really sore, going back into them and holding them for a while. Love it! But I did miss the serenity of a Rodney Yee yoga DVD, just because Jillian talks and talks and talks . . . lots of it helpful to getting the poses right, but still, not totally peaceful. She did make yoga into a real workout though.