What are the real-world problems with Ruby? [closed]

Question

Ruby is a great language. It's fast and flexible, and reminds me a lot of Python of which I'm also quite fond.

Ruby is also very popular, and has been for a few years now. Now that there are some "real world" projects and "rails-app businesses" out there, my question is this: What are the problems with Ruby? What are the things that is doesn't do particularly well? Are there any other products or technologies that have proven particularly difficult to deal with when integrating? Before embracing Ruby for mission critical apps, what are the things that should cause developers to pause and take caution?

Furthermore, has anyone compiled a list (blog-spam or otherwise) of some of the main pitfalls of production Ruby development and how to mitigate those risks?

EDIT:

By "real-world" I mean business world, as opposed to the academic world where there are no budgets and timelines.

Answer 1

There is an article titled Lessons Learned in Large Computations with Ruby, it's worth reading.

Answer 2

Ruby isn't fast. It does have other qualities, but if your CPU is any sort of bottleneck (which in many webapps isn't really the case), then Ruby is not a suitable tool. The current "standard" Ruby doesn't even compile to bytecode (like Python does, for example), but interprets the AST instead, which probably puts the slowdown in the ballpark of 20-100. However, this is probably about to change (or at least get better) with Ruby 1.9. And JRuby, which is JVM-based as you surely know.