In classic Rarst form, when asked what he'd change in WordPress: “I have no interest to change WordPress left. I learned to let it be what it wants to be and not worry about it.” And in response to what threatens WordPress: “WordPress is a main threat to itself.”
He also released survey data he collected from developers in regard to their familiarity and happiness with various WordPress APIs. Of 67 developers surveyed, the average API got nearly 3/4 neutral or positive response, but not all APIs are loved the same. Rewrite rules topped the list of least favorable API.