Something surprised me as I was giving a try to the new trackBy feature.

In the following example, an array of users is generated every second with two users (always the same names) and a random score for each one.
The ngFor is used to display the list of user with their score.
trackBy can be useful here to track the user by their name rather than by their reference (which changes every second).

But if we do this in Angular 2 beta.3, the score is never updated.
Is it on purpose? AFAIK, in AngularJS 1.x, that was not the case (the score would be updated even if the ngRepeat was using a trackBy).

@Component({
  template: `<div *ngFor="#user of users trackBy userByName">{{user.name}} -> {{user.score}}</div>`
})
class TestCmp {
  users: any;
  constructor() {
    window.setInterval(() => this.users = [
      {name: 'user1', score: Math.random()},
      {name: 'user2', score: Math.random()}], 
   1000);
  }

  userByName(index, user) {
    return user.name;
  }
}

cc @kara @mhevery