I have been a Curves member on and off for YEARS. If you are a couch potato I would HIGHLY recomend it. If you are a fairly fit person who eats well and isn't too over weight, I honestly wouldn't recomend it. I am a borderline couch-potato and really enjoy Curves for the first 6 mo to a year. Here is the deal with Curves: its a curcuit training setting, with machines and running boards (which you can do whatever you want on). You get what you put it an Curves, thats all there is too it. Typically 2 rounds is right at 30 mins....I usually do 3 rounds for a little extra. I also am a big fan of stretching afterwards and some extra crunchies etc. So I alot about an hr for a workout. Anything less is just not being reasonable in my opinion. You can not buy into the whole "30 min" workout....if it sounds too good to be true it probably is! But if you go there, keep your heart rate up the WHOLE time and go 3-4 days a week you WILL see results.
The other thing to keep in mind is that everyone looses weight differently. Some people HAVE to diet to loose weight, others working out does the trick. So if you dont loose wt etc, it may not be Curves' fault. I can tell you that even if I dont loose massive amounts of weight at Curves, I ALWAYS tone up and loose inches. I also feel GREAT when I leave there. Working out gives you crazy amounts of energy and is just good for you.
Some reasons I like Curves...I dont have to "dress up" to go there. Its all girls who dont care what you look like while working out. The women you workout with are all generaly very nice and you become like famlily a little. Its never so crowded that you have to wait etc...I HATE waiting on a machine at a gym. The downsides to Curves in my opinion: no daycare option, no pools, no locker room area.
If you have any more specific questions feel free to ask away : - ) Hope my insite helps a little! Good luck : - )