Just my two cents...I have been working out at Curves since September. When I started, I was only three pounds away from my goal of 175 pounds. Since joining, I have lost 12 pounds and 30 inches.
When I workout, I focus on the machines and work them as hard as I can. By the time 30 seconds on a machine is over, my muscles are ready to be done. If you are not feeling a workout, and that is what you are looking for, you are not working hard enough. I use ther recovery stations for just that, recovering. At the end of my 30 minutes, I feel worked out.
If you think that the instructors encourage repitition over form, you were not trained correctly. When you start, you should be taught how to correctly position and use the machines. After you have gotten the form down, then you increase your repititions to your comfort level. For some, that is just getting moving, for others, a nice steady pace, and for even others like me, busting a** for a really good workout. Our Curves always has someone on the curcuit to remind members of the correct position/form to use the machines correctly.
Just so you know, I was not a beginner to exercise when I joined Curves, and I still saw results. Heck, I still see results (though not as rapidly) each month. I joined not just for the workout, but the all ladies aspect, the limited amount of time I have to spend there, and the social atmosphere. I also like that I can go to any Curves, anywhere.