The thing is, Category Theory and the practice of programming are too far apart. To create a reasonable application of some notion of CT in software development, the notion must be first thoroughly digested by the theoretical computer science, with the usual stress on the computational efficiency and the constructive formalism; the result of this must be a set of well-understood computational schemes - data structures and algorithms; only then one can hope to arrive to a design of a universally useful library, in a given programming language, that could withstand criticisms and the test of time. This is similar to the distance between, say, knowing Analytical Mechanics on the one hand and being able to build an efficient and economically viable internal combustion engine on the other...