A lot of pure-Ruby people don't get how powerful this is.<p>My startup, which will have an early alpha up at the end of the month, leverages a lot of JRuby's easy Java integration features. Solr, for example, has been a big win for us -- I've written a Rails plugin that ties to an embedded Solr server, and because there's no network overhead, search requests on indexed data finish up in under 30ms before the cache has warmed up, and 1ms once the index has been cached.<p>On top of that, the JVM (with JRuby, Rails, a database, and Solr) uses less than 200M of RAM even when being pounded by our benchmark suite, and produces impressive performance results... even when running on my laptop. On a full-fleged server machine, the numbers are even more impressive.<p>And all of this, without having to write a single line of Java. It's a good time to be hacking on Ruby.