I’ve been using it in a decidedly industrial application for about 1.5 years now. I had some fairly significant experience with it prior (https://github.com/mattgreen/hython).
For the first time in a long time (20 years experience) I’ve needed to learn a significant amount of things. It’s a combo of the domain and the language. It’s rather exhilarating, and also exhausting. Could also be a lot to bite off on with a busy home life too.
Regardless, the language is brilliant. My manager exhorts me to generally write in a top-down manner a lot because Haskell’s flexibility really conveys dev intent well, so think hard about how it should read, and start from there. This is a huge mindset shift from most langs, where you can feel your brain shut off to save cycles as you type “function” over and over. It really feels like it is meant to be write-friendly. Point-free functions are wonderfully terse to write. I joke that TH is my favorite language: a type-checked macro language that lets me write almost anything I want.
And there’s the rub: even with controlled effects via monads, the syntax is still hard for me to scan and read. I don’t know if this comes eventually or what, but this feels like a function of how dense a line could be. I miss early return dearly, and understand why it isn’t a thing (except if you have a MonadZero at hand) but I know it’s a syntactic transformation that won’t make it in. I really miss the amazing Rust LSP. Haskell’s recently lost the ability to flesh out pattern matches due to Haskell internals shifting with 9.x. I still hate and screw up stacking monads. Compile times can be brutal, esp if you hit the lens library. Finally, I’m not a big fan of pervasive laziness: the community has sort of admitted that Haskell programs are far more prone to space leaks developing from this default to the point that many programs may have them go undetected for quite awhile. The systems programmer in me screams out.
I really think the community is one of the strongest group of programmers I’ve ever seen. I don’t want to belabor this and dwell on the big brain memes, it’s more that they think hard on this stuff and actually push forward, vs just telling each other that web frameworks are rocket science and it’s impossible to do better than what it exists.
Ultimately, Haskell fits like a glove for our domain of program analysis. Beyond that, I’d still be a bit wary. I’m still thirsty for a PL that is essentially OCaml but with a better syntax. But that’s just me.