Ember.js has a distinctly different feel. Yehuda Katz and Tom Dale are two brilliant and influencial developers, but more importantly they are both very nice guys. The culture of an open source project feeds from it's founders and as a result the Ember.js community is also very open and welcoming. Open source needs to be "open". That seems like an obvious statement. However, just opening your source code isn't enough anymore. You must be open in the sense that everyone is welcome to the party. I like that the Ember.js accepts as 'core' contributors those who write documentation and plan conferences. Ember.js may have been founded by a couple of really smart guys but their vision has allowed a code base to grow to a movement now owned by a world wide community of individuals with diverse backgrounds and perspectives. That's powerful.
Even today, I find myself falling into the trap of unwittingly isolating myself and even our team as we try to solve complex problems. We worry about performance. We worry about architecture. We worry about long term maintainability of our projects. We worry about best practices for organizing and deploying our code. We forget that everyone else is worrying about the same problems. The Ember.js community has chosen to combine efforts and worry about these problems as a group. The result is that we can solve the big problems once, commit the solution to code and share it - openly. Ember.js provides not only a convention for writing and organizing our code but also a framework around which we can unify our discussion about the bigger problems the development community faces.
We've spend the past year buidling Ember application for a diverse group of clients many of who are smaller organizations and startups. They look to us to make the right technology choices for them. They can't afford the wrong choices - they don't have the money to re-implement the solution. Wrong choices put them out of business.
I'm glad to say that we've made the right choice.