Ask HN: What is a good use-case for Node?

This is an honest question here.

First, I love Node / JavaScript. That very clear C-like syntax makes everything very readable (also interested in Go, C, etc) and as long as you use named functions for callbacks you can rather easily avoid callback hell. It is an amazing tool for quick prototypes and toying around with things (TCP, UDP, etc). I also realize it has some flaws that can't be ignored. It isn't very fast. I have no evidence that it isn't riddled with security issues. With enough requests you can crash hard.

While some of these things can be mitigated to some degree I'm seriously wondering what a great use-case is?

I use it for simple websites and APIs mostly and then some IRC utilities / bots as well but what does HN think?