After been doing some coding on the HP-35s I wrote what I called 'A programmer's HP-35s review' in my blog:
http://aha-hp-calcs.blogspot.com/2007/10/programmers-hp-35s-review.html
Main message: Found RPN, vector type and equations in programs to be very powerfull.
I am not familiar with RPL (yet, there is a 50g out there with my name on it :-), but I have the feeling that the possibility of using equation in programs on the HP-35s perhaps makes its programming language something between pure RPN and RPL, RPN+ :-)?
Anyway, its been an interesting 'return to HPHC programming' since the long, long gone days of HP-41 hacking!