>I tested using both positive and negative priority and your directive always ran first. I *did* get it to work by changing your formatter to:

>                    function bind() {
>                        return ngModel.$formatters.unshift(function (value) {
>                            return format(value);
>                        });
>                    }

Don't know why the priority approach didn't work but this shows that your formatter needs to be first in the $formatters array.....

There is some activity in the issue I raised

https://github.com/angular/angular.js/issues/11157#issuecomment-75706528

and I also posted a new plnkr

http://plnkr.co/edit/z1BWMoPmnsCZlAUra0os?p=preview