In case you didn’t hear this a couple weeks ago, Oracle published their first JRuby on Rails application as a top level domain on oralce. The application is called Mix, and although I am not exactly sure what it does, it does seem that the same experience that happens with most Ruby converts happened with the devleopment team for Mix. Rich Manalang was a lead on the project and he recently published his thoughts, sort of a post-mortem, on the project.
Some interesting points I found, was that he actually developed in C-Ruby. Now this wouldn’t work very well if you needed to interact with Java libraries, but for most Ruby development it will probably work quite well. Also he mentioned that he went in not believing that he could accomplish the task in the time provided, but he did.
All in all I think it is a big win for Rubyist who want a foot into the Java world.