I've been at a Curves, wasn't bad I actually lost a lot of weight and the machines really help u to push yourself. After the workout u can go to a computer and see exactly what muscle group you worked out. Green is good, Orange is okay, and red means you were lacking.
Only thing about curves was that everything works in a circuit and if you have been there a long time it tends to get boring, doing exactly the same exercises in the same order every day.