Haskell shines at large codebases. It shines in a lot of other domains, but there's no mainstream competitor on dealing with messy, badly defined, big, changing problems.
Haskell shines on refactoring, API designing, and constrain setting (want to enforce safety? atomicity? thread ordering?). As a bonus, it'll also reduce your codebase an order of magnitude or two.
I mean, yes, if you never wrote a complex parser on Haskell, you should try. But that won't change your life too much.
Haskell and its advocates talk a big, big game about its supposed strengths in these areas, but there are suspiciously few examples of these strengths actually manifesting in anything but toy or academic projects. I've been hearing about Haskell's supposed miracles for years and years, and I've never, never seen them.
Many things that emerged at Facebook during recent years can be attributed to the influence of Haskell. React, Immutable.js, GraphQL, etc. Haskell is extremely powerful but allow me to rephrase Euclid "There's no royal road to functional programming". If you want something more pragmatic, yet still quite expressive and powerful - try Clojure and Clojurescript. Especially Clojurescript - it's probably one of the best languages out there to use for front-end and mobile app development.
A lot of stuff happens behind closed doors. Standard Chartered Bank has 1.5 million LOC of GHC Haskell and another 1 million LOC of their own internal Haskell implementation.
I'm also aware of another 5 or so big banks having/building Haskell teams for developing internal tools, but all this stuff is hidden. The biggest, public, project I'd say is FaceBook's Haxl (as pointed out elsewhere in this thread).
Standard Chartered is the other standard example. The only significant Haskell codebases anyone mentions are Standard Chartered, Haxl, maybe Barclays, and the GHC itself. It's pretty damning.
Haskell shines on refactoring, API designing, and constrain setting (want to enforce safety? atomicity? thread ordering?). As a bonus, it'll also reduce your codebase an order of magnitude or two.
I mean, yes, if you never wrote a complex parser on Haskell, you should try. But that won't change your life too much.