I really liked Curves for two reasons:
1) It was a great beginner workout. I was not 'over weight', but I was not in good shape. It got me going.
2) The main reason I thikn #1 was true was because it really is half an hour. When I went, a few years ago, it was about $50/month. There were small changerooms, and one smallish size circut workout room - thats it! Nothing to keep you dillydallying (i.e. showers etc) So it really is IN and OUT! I liked that - although $50 for no very much.
There is a circuit with machines and pads between each - so everytime there is a beep in the music, you rotate. If you are already into working out in some capacity, I would think this is probalby not for you.
After joining Curves for a year, I switched to Goodlife. Their classes are awesome and fun. There is also more variety. The hours at either Curves of Goodlife for WOMEN aren't great though. Goodlife isn't much more expensive than Curves.