Recs.
Updated
Specs
Pros
Pro Uses Handlebars
Ember's preferred templating language is Handlebars. This is mainly because Handlebars is a logic-less templating language and Ember tries to keep it's logic outside the view.
Another reason why Ember benefits from Handlebars is mostly aesthetic as Handlebar's clean syntax makes for easier to read and understand templates.
Finally, Handlebars templates are compiled instead of interpreted, which means that they are much faster to load.
Pro Opinionated in terms of application structure
Ember already defines the general application structure and organization for you. This was done to prevent developers from making mistakes which would needlessly over-complicate their application. While it's still possible to go out of these practices forced to developers by the Ember authors, you still have to go out of your way to force them.
Pro Excellent API
Ember's API are really easy to understand and work with. It has methods which allow you to harness complicated functionalities in an easy to understand way.
Cons
Con Very opinionated
Ember (and many extensions, like Ember Data) force the implementation down specific architectural paths. These paths are what Ember believes is best practice and typically are fine, but not in all cases. This can occasionally lead to fighting with your framework which is never productive.