The one issue I've already had with RPN is that you require a separator between numbers anyways - in RPN it's too easy to parse "23 4 +" as "2 34 +", for example, especially if you're writing quickly.

On the HP calculators the separator would usually be the enter key. I think the old ones displayed just the top entry of the stack, on the newer ones with bigger display you see the stack with each entry on one line.

Might have been better to demonstrate that using subtraction as addition is commutative and thus either one works fine in this case.

One is 27; the other is 36.

LOL, apparently I suck as a parser. I read them as just swaps of the numbers, I.E. 23 4 + vs. 4 23 +.

I learned it for some scholastic competition once. You're right, after the initial confusion, it was fast and intuitive.

I've forgotten it all now, of course. How often do I need to calculate something?

I know that feel, bro. ENT > =!