I personally have never tried Curves, but I've talked to many who have, and I've read a lot of press coverage about the chain. If you're into workouts a la Cathe, Curves will make you laugh out loud. It will not be challenging enough for you down the road.
I have a few thousand personal and professional issues with Curves, primarily because it is entirely market-driven rather than driven by safe and effective exercise principles. The staff at any Curves facility almost never have any background in exercise science, and indeed you do not have to have any background in exercise science to open up a Curves franchise. Instead what you do (at least the last time I read about it) is cough up a lot of dough, and go to a 5-day training seminar that includes precisely one day of exercise science. That's laughable, and dangerous when you consider that Curves markets itself to a beginning exercise population that needs all the good guidance it can get.
And the ignorance of Curves staff can be frightening. I read a post a few months ago on a forum for fitness professionals that I frequent; this Curves staffer stated that the Curves workout (at least in terms of the resistance equipment) was a lot like water aerobics because the resistance equipment is hydraulic. That is kind of like saying a golf club and a gun are a lot like each other because they're both made of metal. Aargh.
Save your money, your health and joint safety. Invest in Cathe workouts.
A-Jock