How good is a trampoline as a form of exercise?

Trampolines are a terrific workout toolIt's actually terrific, if you do it for long enough and in a consistent way. Unlike jogging or working on an elliptical machine/bike, it incorporates not only an aerobic workout (when you do it for long enough), but also spacial coordination -- training your muscles to more with precision and balance so that you can jump with maximum accuracy. Also, it forces your muscles into more aggressive stretching positions as the impact is fairly intense if you jump high. Each time you jump (and some people do it with weights to increase the challenge), you're actually exercising the entire body -- abdomen, shoulders, pecs, back, thighs, calves, etc. Most forms of exercise are limited to just one or two of these.

If you have a knew injury that keeps you from jogging or other sports, a mini-trampoline is often a way to cushion the impact.

Trampolines are often considered a better way of exercising than treadmills and other forms of gym equipment, this is because they require the use of more musles and they are more enjoyable.