I love RPN! I got used to it while my Engineer-Studies in Germany, around 1992. I got an HP 48SX an it was a hard time to really understand this RPN. But when you checked it, it was boosting my Math-skills. Because to work properly with RPN you MUST understand what you are doing. it's the exact mimic of calculating with pen and paper. If you don't understand what you are doing, you are doomed. And so i have to understand what i was doing, which was very supportive to learn math the right way! By the way, the most funny part of using aa RPN machine was the fact thats Students which wantes to lean my Calculator gave it right back after trying to use the thing the algebraic way.