I've settled on Go to replace a worn out Java mess (otherwise a Python shop). We need the computational performance, and I do like the general feel of the language. I think this is something you're going to see a lot of going forward. It's the same niche Scala has been filling to an extent, but I personally think Go is a much better option (unless you need the JVM of course).
You might have misunderstood the parent, I think. It seems like he was saying that they used Java (and then Go) in lieu of Python because of the performance.
But to answer your question, the Language Shootout seems to suggest Java and Go are on the same plane in terms of speed. Take that with however many grains of salt you like.
It's also interesting that according to the Language Shootout Go uses a fraction the memory of Java - meaning you can save a lot of money by deploying it on cheaper machines or VMs and get similar performance to Java.
I just checked out the language shootout. Go has really pulled ahead from where it used to be. Faster than SBCL or Ocaml or Free pascal on quad core 64-bit - that's impressive.
I can use Scala and not pay that penalty. I'm looking at Go to replace components of my system where I don't want a full bore JVM, but I have to be thoughtful about latency. I prefer C for this (C++ seems to be the standard there). Would love to move to something like Go once I can.
