Todd Motto:

The key concept behind these performance considerations is reducing the number of $$watchers inside Angular to improve the $digest cycle’s performance, something you’ll see and hear more of as you continue working with Angular. These are crucial to keeping our application state fast and responsive for the user. Each time a Model is updated, either through user input in the View, or via service input to the Controller, Angular runs something called a $digest cycle.

Deckt sich mit meinen Erfahrungen bisher. Wer Angular 1.3 noch nicht nutzen kann/darf, sei als Ersatz für ::value auf bindonce verwiesen.