I'm working at an extreme programming shop, doing pair programming in perl. Most of the nifty emacs ideas came about while pairing. i.e. your pair says, "Lets go see how 'munge_data' is implemented." If it takes thirty seconds to get the method on the screen, it really breaks up the flow of the session, and you lose focus on what you we're doing in the first place....

So, to answer your question, I've been at my current job for a couple of years now, and really only got into the highly-customized emacs craze within the last year or so... The configuration consists of a bunch of lisp functions, and some small perl utilities that get invoked from the lisp to handle the really tricky parts.