I see a lot of comments on usability of HS in Prod. We @ juspay.in use it to power a bulk of UPI payment transactions. We also use PureScript to power our payment page SDKs.
API (CRUD/Auth) code written in HS becomes a beauty once you start building experience with HS. I think the most advantage of FP comes from how it changes the way you model your solution for a problem. With a strict type system, it's easier to anticipate edge cases and with currying building abstractions becomes natural.
Having said that, HS is not all sunshine. It took me an inordinate amount of time to setup an IDE like environment. If I recall correctly, HLS would take > 20GB of RAM in few hours with our code base. Eventually I had to remove that and extensively use only the editor features to jump around code.