Disclaimer: I've been using Ember for quite some time now, about when 0.9.8 was released, which means I'm not a random hater using backbone or angular.
I do believe Ember is the best thing out there, but I want to point out some things which really piss me off.
Most of them are based on the fact that the core team doesn't seem to be organized and doesn't prioritize the right things. Here are couple of examples:
- Ember Extension was a great idea, there were couple of videos released with it, everyone loved it, but the project has been dead for 2 months now. There are 11 open issues, many of them for a few months without any response from the core team.