I couldn't agree more, but I think you should add Clojure to the list. There's also advanced profiling tools available for the JVM platform.

For those who do use Rails the Torquebox environment is available http://torquebox.org/

TorqueBox 4's web server is powered by Undertow. Check out the performance benchmarks: http://www.techempower.com/benchmarks/#section=data-r9&hw=i7...

undertow edge 183,150 requests per second on the JSON benchmark