I'm convinced a large part of the benefit people see from RPN calculators is that you have to figure out the order of operations before you start. It forces a way of thinking about the equation which is less error-prone, you're more likely to notice mistakes as well.

Takes a little getting used to, but the interesting thing is that analyzing an equation for the proper order of operations on an RPN calculator is not at all an error-prone process. It's a careful process, and it forces an understanding of the equation itself which just churning through it on an infix calculator does not.