Do you really pick your language by your perception of its users? I'm not sure that's a great criteria for choosing a tool. If an annoying dinner guest admired the butter knives, would you butter your roll with a fork?
Concrete example: The Ruby community is very focussed on the Web, so there's Rails but they aren't really interested in scientific computing so there isn't a real equivalent to NumPy.
I'd mod this up more if I could, because this is the best answer to the original question.
The important thing is the community, not the language. Decide what your problem is, find the people who are working on that problem, and use whatever they use.
The importance of community is the reason why the number of people who praise Lisp as a language is so much larger than the number who use Lisp every day: The Lisp community is small, unfocused, and arguably broken. Meanwhile, I work as a professional Drupal developer and am (god help me) gradually becoming an expert on PHP, but that has nothing to do with my nigh-nonexistent respect for PHP as a language. I do it because the Drupal community is large and growing larger, it includes as many noncoders as coders, and it's focused on building websites rather than obsessing over tools. The result seems to be that customers like using Drupal for their sites. Rails and the like are focused on making programmers feel empowered, but Drupal is focused on making site admins feel empowered.
I was reflecting on the original poster's comment:
"But there are so many really enthusiastic posts about Ruby and while Python has a lot of users and is very popular and successful I rarely see anyone rave about it."
It was a poor choice of words on my part - I meant to characterize that evangelism doesn't necessarily mean it's a better tool. I was reflecting more on his commentary about "enthusiastic posts" in my comment than any personal opinion on Ruby ( I find a bit of zealotry in the Rails people but that's neither a bad thing nor is it my place to comment on it). My preferences tend these days towards being slightly turned off by the loudly evangelised toolsets, simply from past experience of what happens to the communities when they get like that. After things calm down, and the happy masses move on to the Next Big Thing(tm), the languages, tools etc are often quietly solidified and iteratively improved (uncelebrated, in many cases) by those that stick around.
I recently came back to Perl, having joined a firm building systems in Perl, and was surprised at how much has happened in Perl in the 4 years since I stopped working with it. While so many of those that formerly evangelised about Perl moved on to Ruby and Python, the people who were forced to continue working with it every have found ways to improve it. Adding a try/catch syntax with proper exceptions, and similar constructs (albeit a bit Monkey Patch-ey) have made it much easier to work with.
It will be intresting to see what happens to Ruby when the Next Big Thing happens, and the community sheds a lot of it's more fickle members. That's not to say Ruby isn't a fantastic tool now, but I'm interested to see the maturity that comes from the difference between those who think it's really the best tool for them as opposed to the tool that everyone loves.