Oh yeah, I totally agree, the examples for the IO monad match up very well to what can be done with Promises. My point was more that this is the case because the IO monad is the canonical black box monad: All you can do with it stems from its implementation of the monad interface, and so anything that behaves like a Monad will look very similar. This is tantamount to saying that Promises have a potentially useful Monad instance (which I am completely in agreement with you on).

The point about continuations is also a very interesting one, but I think again, stems from the same idea: Almost any monadic interface can be simulated with continuations.