[nailer]

If you solve callback hell for a series of sequential functions by using an actual series of sequential functions, you don't have nested callbacks and you didn't require Promises or composition - just a basic understanding of data structures and first class functions.

It seems you're defining callback hell as 'whatever promises solves' rather than it's common definition of over-nesting.

[spion]

Callback hell is a "loss of composition" problem. Most languages, including JavaScript, have things called expressions. Expressions rely on functions returning their output. They become useless when functions give their output through a callback passed as their input: they don't compose with that frankenstein.

Node style callbacks are a prime example of how in the quest for "simplicity" and hate for abstractions its easy to build a monster / frankenstein like caolan's async. Node callbacks were a self-contradicting philosophy: it abandoned all thats already in the language in the quest to avoid an abstraction that was not already in the language :)

[nailer]

Hrm, it's always seemed natural (and not frankenstein) that a function would be input as much as a number or string is. 'My name is Steve, my age is 7, and here's what do to one the database has saved'.

That said I see how the inconsistency you're talking about with how expressions return values with callbacks and you've certainly put the point very well.