Yes, writing Haskell definitely takes a mental context switch. You kind of have to abandon the traditional style of programming in order to transition into it. Pretty similar to what writing Prolog feels like for example. In contrast, it seems like there's a more direct line between languages like OCaml/Lisps versus C/Java.

I like to liken it with muscle atrophy. Gotta get my weekly fix of Haskell to maintain it!