Computed properties are a good workaround. Getters and setters could be better though. That way no one on the outside of the object needs to know the details at all. Am I right in saying that by sacking off old IE browsers we could switch to getters and setters (as in, native js implementation) already?
Almost.... and Ember can mostly work with that last time I checked.
The missing piece is delegation though, i.e. you can't define a catch-all getter/setter and many Ember.*Proxy classes/mixins (e.g. http://emberjs.com/api/classes/Ember.ObjectProxy.html) rely on that. Like most Ember Controllers are delegating data state to a model, and are supplementing app state/behaviors on top.
ES6 Object Proxies fixes that.
But I'm liking how fast the Ember team has been including ES6 transpilers into directly in to Ember App Kit. So we may be writing more regular JSy looking property dot notation, like Angular, soon enough. And get all the benefits of UAP.
(By the way, for coffeescript fans, ember-script sort of does this for you: http://emberscript.com/)