The $watch on scope.options inside of onInitialize wasn't firing for me.

Line 106
        scope.$watch('options', function(){
          selectize.clearOptions();
          selectize.addOption(scope.options)
          selectize.setValue(scope.ngModel)
        }, true);

I believe it was because the reference $scope.options in my controller was being overwritten from within angular-selectize here:

Line 92 
scope.options = generateOptions( (scope.options || config.options || scope.ngModel).slice() );

I'm going to submit a pull-request with the changes that worked for me - would like to know what you think. Thanks again for this clean directive, Cheers!