I work so much with APIs I began to gather a list of top APIs by experience and usability. Stripe is right up there at the top of the list, everything about it is just plain beautiful.
I literally paused reading when I read this simply put exact statement. I try to focus on minimal, simple apis and preach it to developers and clients for quick integration and maintenance. Now I have this powerful statement to save hours of explaining mainly to non technical people. I have always thought this but never so crisp and to the point. We need t-shirts. Doing a quick search of Google, it appears a few others have recently stated this as much but it is an idea that should take hold: http://www.kryogenix.org/code/apis-like/
I don't think the topic is new per se, as really a lot of software engineering history has been about dealing with the human aspects of development. Even fundamental concepts like object-orientation are grounded in psychology and even before software, there were precursors for this kind of thinking in the way machines and working environments were designed. Josh Bloch's Effective Java is a more recent example.
The difference now is that UX has become a popular, well-understood, discipline. So we have a lot more concepts to take back into API design.
Some of us have been capturing relevant links on the topic on a Developer Experience page (https://plus.google.com/116834904360889286443/posts) and under the #devexp hashtag. We don't have t-shirts, but we do have a logo in need of much love! I'll go add a link to that presentation too.