I haven't personally used it, but my mommy does. She's been using the Zone system for a little over a month now. She says she hasn't experienced great weight loss with it, but she has definitely toned up.
My mom is no stranger to exercising, and for the first few days after she started, she was ungodly sore. I don't know if she just overdid it or what, but that's something to watch out for.
