It takes many of the good parts of both and wraps it in some very nice syntactic sugar. What's not to like?
However it also adopts a bunch of the bad parts like having variance but not really having a way to handle it. Last I remember the Equatable instance for tuples was just magic, it was impossible to rely on it with the types. Even maybe 6 months ago when I last tried this if you write some code that appends maybe 6/7 arrays together immutably the compiler would go into an exponential spin.
The project I'm working on ending up dumping it entirely and moving over to being a web project written in TypeScript because it was so bad. Part of that being a laundry list of problems with the surrounding tooling like SourceKit which may or may not still apply.