She is a pretty tough trainer, and has a few DVDs and books out. If you have an average fitness level and have done interval training before, you can try her DVDs out. But if you are a beginner, I would suggest Kathy Smith DVDs to build up your strength and stamina before going Jillian. Jillian is more about kicking it into a high gear and very much about keeping the intensity on, plus her commentary particulary on Shred is not very supportive.