Look, it is true that Ruby is not fast like other languages. But the goal is to focus on algorithms, prototyping, delivery, working. Get that going and you make money because you have a product. Afterwards you can translate to Java or whatever when you have the money.

I don't love ruby because of lack of generics in Java. Or lambdas (though that would help in java).

In any case... I say don't ignore it, but keep an eye out for changes in the community. When the Ruby community shifts to another language, thats when Ruby dies.