A developer who is curious enough to try Lisp is possibly more intelligent than average
This is the kind of exaggeration that makes a lot of people to avoid even trying Lisp. Any programming language that uses a different programming paradigm than the one you are familiar with will make you a better programmer.
If you do decide to try a lisp, don't start with Emacs Lisp. It's a mess. Go with Clojure, out of all lisps it's one of the least self-congratulatory about how awesome they all are for using lisp.
Well, Clojure also was a mess when I tried it (2 years ago maybe?). Leiningen (a/the build system) was pretty slow, and I couldn't find a way to use the language in a more lisp-like way easily, like editing a few files and (re)loading them into a running REPL (other than iterating through all buffers in Emacs and loading/evaluating them manually; there may have been other problems as well, I don't remember). You know, like you can edit a few Java files in Eclipse, press shift-ctrl-s, and have the new code hot-deployed into your debugging session.
Maybe the people who wrote the Clojure tutorials considered that question to be SO natural they didn't even mention it, but I found it very unintuitive. And running a very slow tool on every code change and waiting for the build and then starting the program is very unnatural and un-lisp-like.
Common Lisp is a bit old by now, but it's always been very stable and fast. Maybe Racket is a more modern+mature Lisp family member that's nice to try.
I also tried getting into Clojure around that time. I was coming from CL where we have nice things like conditions and restarts, dynamic variables, and CLOS -- being able to hit an error in the debugger, inspect the slot of the instance of some object that caused the error and recompile the class definition to fix the error without restarting the program is really nice (all of the running instances are updated). I was not used to Clojure's unhelpful tracebacks.
I don't understand what age has to do with anything... CL is still a good language.
I'd also say that one might do well to explore it, even if you don't plan to use it for everything. I'm definitely a Lisp neophyte (Scheme in college, no Common lisp, and then ~6 years with some lisp-like proprietary framework), but there are some things I really miss from it.
As some have said, it's worth learning because of the way it can change the way you think about things. It sounds hokey and trite, or like someone's trying to be smug ("I'm in the secret lisp club!"), but I genuinely feel profoundly grateful to have been exposed to Lisp. (To be fair, I also really like programming in Python for _many_ of the same reasons I enjoyed programming in Lisp.)
Yes, it's very cheesy, but maybe rephrase it as "people who are open to trying new languages are more open-minded by definition, and they keep a flexible mind and learn to think about problems in different ways."
I mean, however cheesy some Smug Lisp Weenies(tm) may be, why not learn something new? Lisp (the language family) is really cool, you should try it. elisp may not be the most exciting family member, though.
That quote is taken out of context and was written by someone who's first language is obviously not English. I took the paragraph to mean that Emacs users are possibly more technical because it attracts those who are curious enough to research less mainstream programming languages.
The entire paragraph is about Lisp if you read carefully. The mother tongue of the author is irrelevant, he clearly thinks that Lisp is a superior language for a possibly more intelligent coder:
Emacs is developed by Lisp whose syntax is different from common programming languages. A developer who is curious enough to try Lisp is possibly more intelligent than average. Lisp is often the third language he/she learns (Java/C/C# is the first, a script language like Bash/Python/Perl/Ruby is the second).
This is the kind of exaggeration that makes a lot of people to avoid even trying Lisp. Any programming language that uses a different programming paradigm than the one you are familiar with will make you a better programmer.