As a Ruby dev I am loving JRuby. It is fast, has access to serious app servers like Tomcat and JBoss as well as java libraries, multi-threading like a madman.

I get warm fuzzies when I do load-testing and see the response times go down on a newly booted at as the JIT kicks in.

Plus it works well on windows when I have no choice but to use a windows server.

With new JVM language frameworks like vert.x and the invokeDynamic etc. additions in Java 7 I really really think the JVM is getting some good mindshare in communities that otherwise would not have touched it due to java.