I was a Curves member for quite awhile. It's only 30 minutes and if you commit to 3-4 days a week (plus changing your diet**), you'll definitely see some weight drop off. After awhile, though, I found the routine way too tedious and lost interest. I joined the YMCA which has a circuit kind of like curves, but also the added benefit of a bunch of cardio machines, free weights, pool, etc. so I don't get bored. Overall, I think Curves is a great jump start to getting back into exercise if you haven't been participating in any activities for awhile.
**My Curves did not push a change in diet until after the 1st month of working out. After 1 month, I think I only lost about 2 inches overall and 1 lb. even though I was working out 3-4 days a week, religiously. It was disheartening to say the least. But after I started on their low carb plan, I was losing 2 lbs a week and the only exercise I was doing at that time was Curves 3 days a week so what I was eating was making a HUGE difference. Just wanted to mention this I really believe that what you EAT is much more important than the exercises you are doing. Don't get me wrong, it's a combo of both exercise & diet, but exercise alone did not help me while working out at Curves.
I hope this helps! If you have any more questions, just pm me.
If you want what you do not have, you must do what you have not done.