The async stuff is not really any better performing than e.g. async in C#, which is mature, easy to debug, and has been around a while.

I don't know why people keep saying node.js is "high performance", the numbers I've seen basically put it in the same ballpark as similarly architected apps in other languages, as long as the other language has a reasonably performant toolchain. Perhaps people are used to old Ruby on Rails performance problems?