I haven't bought the Zumba dvd's but go to a local hall with an instructor. The music is loud so you really get into it. I'd have to say that i worked up a sweat after the first dance, and i was dripping wet with sweat after the hour was up. A really great workout.
I'm not sure what it would be like doing it at home though. I take my almost 3 year old with me - she can sit and watch or get up and jump around if she wants. Maybe look into classes in your area?