Ember felt very Rails-y to me. The ember community felt entrenched in rails, and rails is reaching end-of-life. It is old-school thought. Ember made existing ideas better, a 2x gain maybe. I want new ideas, the 100x leap.
I have! Karl and I made this: http://www.hyperfiddle.net/ Not possible to build on ember. React.js in May 2013 was final missing piece that made Hyperfiddle possible and our first commit was in Dec 2013.