I find I
can't use anything but an RPN calculator now. It's just so much
 simpler once you've learnt it. That's why I have a few dozen HPs (LED and
 LCD models).  
   I recently came across a good site that describes how to use one:
        
http://dspace.dial.pipex.com/town/square/gd86/slides.htm  
I remember reading the HP41 user manaul for about 1 hour some 20-odd
years ago, and thinking 'This is obvious and beautiful'. I never went
back :-)
   and I've been having fun using the one slide ruler I have, getting a feel
 for how to use it.   
Several books on slide rules have recently been reprinted. I really must
learn to use one quickly (I understand _how_ they work, and therefore how
to use one, but I don't know all the tricks).
-tony