I worked with Ember for a few months and I like it a lot - it definitely deserves more recognition. One thing that frustrated me a lot in Ember was the run loop. The docs suggest that you don't have to worry about the run loop at all and its merely an implementation detail, yet we had to constantly us Ember.run, Ember.run.schedule, etc. all over the app. But of course in order to know which Ember.run methods to use, you end up diving deeply into the implementation details of the framework itself.