Answer by Samer Buna:
- Big learning curve, it's definitely not for everybody.
- Opinionated framework, for some people, this is a dark hole, even when the opinions are good.
- EmberData is not ready for production yet, it might be that this library is just few years a head of its time.
- Too much generated code, if you don't understand why it's being generated, you certainly see that as a problem.
- 2-way data binding in general has lots of criticism on its own (this is shared with other frameworks of course).
- Routes are the front-line, some people don't see the value in that.