What we are discovering is that actually it doesn't sacrifice as much as you'd think - and I think that's the point we are trying to make with our article.
You get both the performance, and you get a very lightweight language - I'd say almost as easy to write as Ruby or Python - with great open source support and growing and with a great community around it.
Many modern languages in any field are almost as easy to write as Ruby or Python, have great open source support and a great community.
If you use Ruby or Python, you get extreme dynamism that makes things like ActiveRecord or dealing with external semi-structured data very easy (though you pay a performance cost).
If you use OCaml or Scala you get a lot of control over effects, making the code very safe and easy to reason about. And the type systems let you pull out high-level patterns in your code without going crazy, even when those patterns are very abstract, resulting in more concise and maintainable code.
You get both the performance, and you get a very lightweight language - I'd say almost as easy to write as Ruby or Python - with great open source support and growing and with a great community around it.