[nupark2]

However, speed of execution does not matter when your development speed drags. When you are developing a product, you need to be able to move fast.

However, the JVM doesn't necessarily mean 'Java'. If you get free performance and more efficient development, there's no advantage to using a poorly architected inefficient runtime.

[angelbob]

You've pretty much nailed why JRuby catches on so well. It's still not fast for a JVM language, but it's blazing for Ruby - plus you can call through to Java where you need/want it.