Hi Mel. I'm not a doctor. (I don't even play one on TV.

) But any exercise you do that gets your heart rate up for a sustained period of time is a good thing. It sometimes helps to vary the exercises, just to prevent boredom and to possibly use different muscle groups. But you need to do whatever you enjoy doing, otherwise, you're more likely to quit after a while. The only thing that you might want to watch out for is the strain on your knees and other joints. Some people do better without the step aerobics because of the strain to the knees. Personally, I do better walking at an incline at a fast pace, because jogging hurts my knees.
Enjoy the workouts (as much as possible)!
Robin