RPN isn't obsolete as long as you (and other guys) use it.

I believe, it's the fastest method of entering short calculations and it's stack architecture (especially with an unlimited stack) allows for faster execution of programs (on a comparable machine). If you enter your expressions for example on a HP48 you'll even have a command stack (the whole expression lies on the stack then. This is a common practice for me. I enter the calculations in quptes with the space key between the operands and push enter twice when I'm finished.

So I have a copy of my calculation on the stack and can repeat similar calculations rather fast or correct some input errors.

I got used to RPN after using TI calcs for years, then I bought a HP-71 (which isn't a RPN calc). I bought then a HP-48SX and use it til now.

I feel it's much to strong for my daily needs, but it's a very comfortable tool, when I have to do some programming.

Naturally, I use my BASIC programmable 71B, when there are really important things to do :-) (no flames please)