there are plenty of women who have gone and who have lost weight and are very happy with it. that's a fantastic thing! on the other hand, the american council of exercise has done research on the curves curcuit that shows that the curcuit has a very minimal calorie burn, and based on heart rates and v02 max measurements there is little room for cardio vascular improvement. another downside is that there is little room for growth. also, using only machines for weights can lead to pattern overload syndrome, since you are stuck with one plane of motion using a machine, and stabilizer msucles are not used. however, if you have never worked out before it may be a decent way to start out.
one thing that bothers me as a personal trainer is that one workout is not the right workout for everyone. i design people's workout programs based on their goals, experience, needs, abilities, preferences, etc. i have never made 2 workouts the same because no 2 people are the same. that's something that bothers about a place like curves. but don't think 'm trashing it! a lot of women really love it and that's great!
sarah