I joined Curves a couple of years ago and at first I liked it but it got boring very fast. I'm not sure if you know how it works but its basically a group of machines in a circuit with warm up stations in between. You go around the circuit twice normally in 30 minutes, spending 30 seconds on each machine and in between station.
The different machines use different parts of your body eg: legs, arms etc. The machines themselves are great because they are hydrolic so you dont have to change weights etc, but 30 seconds to me just isn't enough.
This is just my opinion, alot of people love curves.