I am very interested in Python for programming on the JVM, and I've worked in Java and Ruby (not JRuby) a lot, and to a certain extent in Groovy.
What are the limits to the Java-Jython and Java-JRuby integration right now? What about Groovy: are there any things that a Java class can do that a Groovy class cannot? And what about IDE integration (mostly Eclipse, but IntelliJ and Netbeans are also interesting)?
I'm not interested in whether Python, Ruby or Groovy is better/more-concise/whatever. I'm just interested in how well they are working in the JVM and tools (especially IDEs) right now. My main interest is not inside a web server, if that matters.
Simple examples of getting a HelloWorld which extends a custom Java class and implements a custom Java interface would be very useful to me.