I have one of those big exercise balls that you can inflate, they are popular with some gyms... I recently started leaning on it for back support and doing dumbell squats, I got the most incredible workout from it, and could barely walk for a few days... so I know it works,.
I like using the ball cause it prevents me from falling over, and I can put my legs further away from my body, kind of the way you do on a leg press machine... then I can bend down without my knees being over my feet..
But is it okay to do squats this way, or is there a disadvantage? Is this better to have back support, or is this weakening me in other areas?