The point of having the spec is that libraries can freely exchange data and promises, even if they depend on totally different flow control libraries, while sti

The point of having the spec is that libraries can freely exchange data and promises, even if they depend on totally different flow control libraries, while still being certain that error handling and chaining works as expected. It looks like if I build on top of your library, I'm locked in. This is not to say that it invalidates your library or that every promise library has to comply to A+ or that A+ is the only good way to design promises in JS.