Yeah, I'd like to see more languages using unicode identifiers. Seems to be a very unpopular approach, though :(
I've seen these things used, but they're not super common. People still worry about not being able to input Unicode symbols in their editor! I personally think this is absurd in this day and age. Naturally, it's very easy to do in Emacs; somebody even wrote a Haskell input mode[3].
[1]: http://hackage.haskell.org/package/base-unicode-symbols-0.2....
[2]: http://www.haskell.org/ghc/docs/7.2.1/html/users_guide/synta...
[3]: https://github.com/roelvandijk/emacs-haskell-unicode-input-m...
EDIT: How many people still have trouble with Unicode input? Should I publish my XCompose solution?