Edit in JSFiddle

var m = angular.module("myApp", []);

m.factory("dataService", function ($q) {
    function _callMe() {
        var d = $q.defer();

        setTimeout(function () {
            d.resolve();
            //defer.reject();
        }, 100);

        return d.promise;
    }

    return {
        callMe: _callMe
    };
});

function myCtrl($scope, dataService) {
    $scope.name = "None";
    $scope.isBusy = true;
    dataService.callMe()
      .then(function () {
        // Successful
        $scope.name = "success";
      }, 
      function () {
        // failure
        $scope.name = "failure";
      })
      .then(function () {
        // Like a Finally Clause
        $scope.isBusy = false;
      });
}

<div ng-app="myApp">
    <div ng-controller="myCtrl">
        <div>{{ isBusy }}</div>
        <div>{{ name }}</div>
    </div>
</div>