Pretty cute syntax, but not what I'd wanted. It takes something that is already trivial to write and makes it simpler. Not a lot of "bang for your syntax bucks" so to speak. E.g the interpreter example from the PEP could have been written:

    parts = command.split()
    if not (0 < len(parts) < 3):
        raise TypeError(...)
    cmd, arg = parts
    if cmd == 'quit':
        ...
    elif cmd == 'get':
        character.get(arg, current_room)
    elif ...:
        ...

For more advanced examples, you'd use dictionary dispatch anyway. Will this syntax work with numpy?