What is the significance of reverse polish notation?
I've used RPN several times for rapid prototyping, e.g. of programs that have to read and interpret a user-supplied mathematical expression.

Whereas regular mathematical notation would require at least a recursive parser (think brackets, operator order, etc...), an RPN parser is basically a stack with a switch-like statement. I guess it's this combination of simplicity and expressive power that led HP to use it initially.

This is, however, usually for rapid prototyping and for convenience. I would never assume that a user can, or wants to, understand RPN.