[dexwiz]

So why Async.js over Promises or Generators at this point?

[megawac]

Promises are great for prototyping, but have significant overhead (http://thanpol.as/javascript/promises-a-performance-hits-you...) for some high performance APIs it may be advisable to use async.

Async also supports nodejs callback patterns which can reduce the need for wrappers (promisify)