I couldn't really rate it properly since I haven't gotten around to using it, but I DID track it down as the cause of a problem with an ajax call on a Drupal site. It broke the site to the point of me spending hours debugging only to find that a browser plugin was the problem. For that reason, I give it 1 star for breaking simple ajax functionality. I hope to come back and revise the review once I have a chance to use it on an ember app.
Tool for debugging Ember applications
The Ember Inspector is a plug-in for the Chrome developer tools that makes understanding and debugging your Ember
js application a snap
View all of the routes defined in your application, Reference Ember's naming conventions for your URLs, Overlay your application with information about what templates, controllers, and models are currently being rendered, Inspect the objects in your application, Make your application's objects available in the console as the $E variable, If you're using Ember Data, see all of the records that have been loaded