> Anyone competent with Javascript can easily read the first form

And anyone competent with any language implementing map can easily read:

    users.map(user => user.name);

...without having to do any "skimming over" the noise. It's not a big difference, you're right, but it's the kind of little thing that, when you let it build up over time, gives you the "write-everything-in-triplicate" feel of Java 6.

Further, you have to be intimately familiar with Javascript to understand why this is necessary:

    function fetchUserData(){
        var self = this;
        userService.fetchAllUsers()
                   .then(function(fetchedUsers){ self.users = fetchedUsers; });
    }

or even this:

    function fetchUserData(){
        userService.fetchAllUsers()
                   .then(function(fetchedUsers){ this.users = fetchedUsers; }.bind(this));
    }

as opposed to simply writing:

    function fetchUserData(){
        userService.fetchAllUsers()
                   .then(fetchedUsers => this.users = fetchedUsers);
    }