I've got it - I'm doing the 30 day challenge at the mo.
I really like it because the work out changes every day so I don't get bored.
I wouldn't say it's the hardest work out I've ever had I'd get a better work out at the gym but I like that I can do it at home anytime and I do work up a sweat (sometimes i do the workout twice if I feel I've got more energy than I have used up)