I'm in my early 30's, go to the gym 4 times a week and am in pretty good shape. At the gym I do the elliptical as well as some of the fitness (weight) equipment. I decided it would be nice to to add some variation to my routine as well as have a workout I could do from home.
I researched for a while and decided on the ball and the video ball workout for Dummies. The result? I'm VERY happy. At first I didn't think it was going to be worth the money or time- I'm used to working up quite a sweat at the gym and thought this workout might be "too easy" for me. Well... not so. It hurt to walk for 3 days after I did the video the first time. This tells me I was working SOMETHING that I usually didn't. It's true, it targets muscles that aren't typically "worked out" on traditional exercises or machines.
All in all, I really like this video. The instructor is a bit annoying but I've come across worse. It goes slowly (which is the point to get an efficient workout) and really explains how to position yourself correctly (which I find to be a downfall of a lot of the others). I'd say go for it!