I did it too, today! I used only a 6" step because am sore from yesterday (mainly upper body). So, I was moving a little slower than normal. I still burned over 850 calories! (Okay, I'm 5'10 and have 20 pounds to lose, but still!). It's a really good little workout, once you get it down. I really enjoy it - especially the last interval.
Shelly - funny - I was thinking that today when I heard that. That is NOT an easy blast. It's fun, but not easy.