Ok ok, mine doesn't include any back whatsoever, and only minimually padded, but it's ULTRA lightweight (under 5 lbs), pretty rugged, and CHEAP PRICED. I purchased mine (a few years back) at a local discount art supply store (Amsterdam Art) for about $18. I spend 1/2 my keyboard performance time seated squarely on the padded seat, yet spend the other half the time leaning againest the edge of the stool for support, while operating the foot pedals with either one or both my left & right feet at the same time. The stool is durable (holding up to 3 years of use & thrashing), especially at such a cheap price, and I never have to worry about it getting knocked about on stage or hesistate to utilize it to fling into the audience if the crowds get too wild. :
http://shop.5click.com/amsterdamart/product.cfm?ProductID=177

Scott