Event bubbling on 3.0.2/latest 3.1 is broken. In the 3.0GA, when event bubbles, event.source contains actual widget that generates the event. In the 3.0.2, event.source it points to the parent widget which makes it useless.
The attached project demonstrates the problem. A parent view is created which contains a single label. A click event listener is set up on the parent view. When you click the label, event bubbles to the parent view. In the 3.0GA, event.source point to the label which has been used to turn border to red. However, in the 3.0.2RC, it points to parent view. So there is no way to tell which object has actually fired the event.