I remember seeing this in a computer store right after the Power PCs were released. My friend and I spent the next hour or so visualizing equations. It was immediately intuitive and powerful, like a TI calculator on steroids. It was everything a school kid could want and played a huge part in buying one of the machines.

While there are certainly more powerful mathematical software applications available today, It's a shame this type of easy to use application (my friend and I figured it out within 30 seconds) seems very rare.