- You can do server side rendering with other frameworks however it is significantly easier and better to do it with Ember.js due to the way ember routing model and Ember-Data works.You can do acceptance testing with other tech stacks however they cannot be as fast as the usual ember acceptance testing stack + ember mirage. Mirage mocks your backend and introduces an in-memory ORM thus your tests wont ever need to hit your backend or the database. This comes with 3 major advantages and 1 major disadvantage:
Advantage 1: Your tests will be very fast. Ember test suit knows exactly when your app starts, it can listen to the next visit, next Ember loop in the Run loop for async functions and execute immediately without timers. These are well defined and documented in the framework.
You can develop very complex frontend applications on the development mode with Ember mirage without a backend. There is a productivity advantage when your frontend developers are not backend developers/not familiar with your backend stack. You can source your backend API responses as Ember mirage fixtures thus eliminate the need for data preparation/model generations with factories for each frontend tests.
- Sometimes you need to write your backend logic in Ember mirage routes. Ember mirage is still an alpha software and all these add up to the learning curve.
Ember.js has lots of potential and a mature ecosystem.
Ember is opinionated, and in most cases that is a great thing. Every other day there's an article about "frontend development is too confusing because there are too many choices", and Ember defaults to making those choices for you. It's not that dissimilar to backend dev, where you _could_ start off with just an http server, and choose your own authentication and bring in your own ORM and in many cases you would have been better off just using Rails. Yes, there are some cases where Ember doesn't fit and you shouldn't use it, but most frontend apps look similar enough and the frontend ecosystem benefits by Ember guiding developers down a well-trodden path.
Another thing the Ember community does really well is its open development process. Anyone can read and contribute RFCs and at any time I can see exactly what's in the pipeline for the future of the framework.