AngularJS 1.3.0-rc.5 breaking example for select using select as and track by.

var app = angular.module('plunker', []);

app.controller('MainCtrl', function($scope, $timeout) {
  $scope.loading = true;

  $timeout(function() {
    populateDBObject({
        id: 3,
        text: 'Three'
      });
    $scope.loading = false;
  }, 1000);

  $scope.options = [{
    groupName: 'First',
    display: 'First - One',
    value: {
      id: 1,
      text: 'One'
    }
  }, {
    groupName: 'First',
    display: 'First - Two',
    value: {
      id: 2,
      text: 'Two'
    }
  }, {
    groupName: 'Second',
    display: 'Second - Third',
    value: {
      id: 3,
      text: 'Third'
    }
  }, {
    groupName: 'Second',
    display: 'Second - Four',
    value: {
      id: 4,
      text: 'Four'
    }
  }];
  
  $scope.simulateUpdate = function ($event) {
    populateDBObject($scope.options[Math.floor(Math.random() * 4)].value);
    if ($event) $event.preventDefault();
  };

  function populateDBObject(value) {
    $scope.dbObject = angular.extend({}, {
      id: 'ffffffffffffffffffff',
      name: 'some record',
      desc: 'this is some dummy record'
    }, {
      value: value
    });
  }
});

<!DOCTYPE html>
<html ng-app="plunker">

<head>
  <meta charset="utf-8" />
  <title>AngularJS Plunker</title>
  <link data-require="bootstrap-css@*" data-semver="3.2.0" rel="stylesheet" href="//maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css" />
  <script data-require="angular.js@1.3.0-rc.4" data-semver="1.3.0-rc.4" src="https://code.angularjs.org/1.3.0-rc.4/angular.js"></script>
  <script>
    document.write('<base href="' + document.location + '" />');
  </script>
  <link rel="stylesheet" href="style.css" />
  <script src="app.js"></script>
</head>

<body ng-controller="MainCtrl">
  <div class="container">
    <h1>Select as and track by example</h1>
    <p>The following select should have "Second - Third" selected, once the 
    database object on the scope is "loaded", even though the original bound 
    ng-model value is <code>{{:: dbObject.value | json }}</code>.
    </p>
    <p>
      <select ng-model="dbObject.value" 
              ng-options="opt.value as opt.display group by opt.groupName for opt in options track by (opt.id || opt.value.id)">
      </select>
      <span class="loading" ng-if="loading">Loading...</span>
    </p>
    <p>This is accomplished by using a <code>track by</code>
      expression that utilises <code>||</code>
      to work for both the model value and the option object in the array (track by = <code>opt.id || opt.value.id</code>
      ).
    </p>
    <p>You can <a href="#" ng-click="simulateUpdate($event)">simulate a random DB update</a> too.
      <p>If you try changing the version of AngularJS in <code>index.html</code>
        used to 1.3.0-rc.5, it will stop working.</p>
  </div>
</body>

</html>

/* Put your css in here */

.container {
  margin: 20px 0 20px 0;
}