I'm not sure I really catch your drift, but:

Using

  {{name}} {{greeting}}

in Ember should have the same effect as

  {{name + greeting}}

in your example, right?

You need not use computed properties in Ember, because updates on ordinary model fields are also updated in templates in real-time (AFAIK works very similar to KVO in Objective-C). Computed properties are just a ridiculously useful concept which allows you to modify/transform stuff before you show it to the user, similar to the view-model in MVVM. How would you show an empty string in Angular with "{{name + greeting}}" if name is empty?