Hi Firmitup,
I have a stairstepper. It's from Bodyguard. I really love it. It doesn't require as much space as a treadmill would, ( although, if I had the space, I would get a treadmill for the ease in which you can do a variety of different workouts.)
My stairmaster has independent pedals, so one leg pushing down does not require the other leg to move up. The spoerts equipment sales person said that this independent action gives you a better overall workout (obviously because your muscles are moving independently of one another instead of relying on the machine).
I do a few different types of workouts on the stairstepper. I do steady state cardio on it for sometimes, and I also do intervals, where I will step for two or three minutes and then get off the machine for a minute of jumping jacks or scissor jumps or some other repetitive hi impact exercise. Then repeat the cycle about 8 times or as many as you want to for that day, then cool down on the step.
HTH
Kathy