Override Rails' jQuery-ujs default form disable behaviour: Keep the form disabled after a successful submission.

rails-remote-form-keep-disabled.js

(function($, undefined) {
  var $document = $(document);
  $document.undelegate($.rails.formSubmitSelector, 'ajax:complete.rails');
  $document.delegate($.rails.formSubmitSelector, 'ajax:error.rails', function(event) {
    if (this == event.target) $.rails.enableFormElements($(this));
  });
})(jQuery);