Does anyone have this? How do you like it? Do you actually USE it and if so, have you seen better results than with other ab exercises? I've always had great abs. Even when I had my 2 c-sections the doctor who cut me open said "jeeze, you have some great ab muscles"! But now I really want to sculpt and define them. I keep seeing the commercial for Bender Ball but I'm wondering if it works or if it will aggravate my lower back issues.