Interesting, I find the ergonomics of transducers a lot better than the threading macros, especially because it’s a more generic interface. Also, they seem to be an ideal point in the lazy/strict evaluation continuum: they compose like lazy functions (I.e. if you have (take 3), you’ll only get three elements even with an infinite input stream but they avoid the unpredictability of lazy functions like map because the actual process is run eagerly (unless this doesn’t make sense for the output datatype e.g. a core async channel.).

I’d also be a bit careful about judging popularity from open source codebases too: they are used heavily in all the production code based I maintain :) and I get the sense that they’re pretty widely used by the “silent majority” of clojure programmers.

My debugging strategy for them is basically what I do for threading macros anyways: (into [] (comp ... (map #(doto % (->> (println :it))) ....) inp)