Elm seems to have a much stronger developer UX story than Haskell (just look at how much better its error messages are than ghc's), and the ability to share dat

Elm seems to have a much stronger developer UX story than Haskell (just look at how much better its error messages are than ghc's), and the ability to share data models across the frontend-backend border would be awesome -- an end-to-end typechecked stack with easy sharing. With Elm on the server too, you could easily implement server rendering to initialize the page for fast load times.