You're way more experienced than me in this, but it seems to me that anywhere you're going to be replacing polymorphism is going to result in more typing. If you know the module that you want, then it is trivial, but the point of type classes (IIUC) is to write generic functions that can act on a variety of types.
To replace the non-trivial cases is going to require pattern matching, it seems. If your types change, then you are going to have to update things in multiple places.
But, like you said, it's not the end of the world. In many cases the intent will probably be clearer. Still, I'd rather have type classes than not.
Typeclasses aren't bad, that's for sure. I kinda want something as flexible as typeclasses and derive generic but no where near that complex. A big part of me says I could do well with just promising some JavaScript really really meets a type signature. Ports are great for side effects but I there might be room for this for pure functions?
To replace the non-trivial cases is going to require pattern matching, it seems. If your types change, then you are going to have to update things in multiple places.
But, like you said, it's not the end of the world. In many cases the intent will probably be clearer. Still, I'd rather have type classes than not.