I have been working with Ember since the SproutCore days. I have watched a passionate, dedicated team spend the last 7 years continually improving the framweork and its ecosystem. Along the way, many things have changed (almost always for the better), but some things have remained constant.
Many of the things I say below have been said by others before. I particularly recommend reading Matt McManus's Improve the interoperability of the community and the framework and Chris Garrett's Ember as a Component-Service Framework.