Yep. Doesn't even feel so different from using error first callbacks. I had to go back to using them for something recently, and feel like most of my problems back then stemmed from excessive deep nesting, and overreliance on the closure scope. Don't get me wrong I love the Promise api, but if ts were popular pre-Promises, we wouldn't have had half the issues with callbacks for concurrency. You'd be able to type functions that take callbacks, know what errors they can receive, see if anything's out of scope or misused, etc