Conversely, I found the experience pretty terrible when I worked on a big cljs/reagent/reframe/figwheel app over the course of a couple of years. It was slow, prone to runtime errors (though not as much as JavaScript), and often presented weird edge-cases at the intersection between the Lisp world and the React world. The company ended up abandoning all this stuff after having been big Clojure/ClojureScript evangelists for a long time.

On the other hand, after having built several large Elm applications, Elm is still the tool I'd recommend. On my current ~10KLOC Elm project, compilation is near enough instant, the structure of the code is more rigid so it's far easier to understand — even for beginners — and there's far less potential for runtime errors to occur.

Of course, this is the classic religious war in programming, so I expect someone to appear soon and point out that there is no empirical evidence to support the idea that a type system like the one in Elm or Haskell results in fewer errors in practice. Or perhaps they'll say jet fuel can't melt steel beams.