Ruby & Java vs JRuby

My team has been doing Java for a long time. We are switching to Ruby. We are finding that Ruby has limitations and that we have to do certain things in Java. I'm trying to find a way to call Java code from Ruby. I'm searching Google and such, and I always end up on a page describing how to call Java code from JRuby. That's not what I want.

Then I start to wonder why we're NOT using JRuby?! Instinctively, I'm thinking Java and Ruby is what we're doing. JRuby is the best of both worlds. What am I missing?

I've asked around a little bit and I've heard a few negative things about JRuby, such as memory issues or diminishing oracle/community support, or whatever. Is JRuby a dud? Or is it viable for real-world, large-scale, mission critical apps, the way Ruby/Rails supposedly is? Is there a reason that we should be coding in Ruby AND Java instead of just going with JRuby? Can we not use Rails if we do JRuby? I mean, why wouldn't you want access to all the comprehensive features in Java, combined with the ease/fun of Ruby?!

Thoughts?