Actually, the dances that they do are really good ab work outs...if they did them correctly! I will admit that I found it incredibly ironic that the "hip hop abs" workout was lacking lets say...the TYPE of people that created hip hop and the dances, but that's another story. If you perform the dances correctly, it is a great cardio and ab workout. But as far as it looks from the infomercial, you may be a bit short changed.
Personally, I love to dance. You could define the type of dance that I like as hip hop dancing, but I do it as a workout now because I am recovering from some torn muscles in my abdomen so lifting weights is out of the question. As I have done dancing to supplement ab workouts, I have found that my abs have developed much quicker than when I was lifting weights and specifically focusing on my abs. Plus, it's fun as hell! Haha