I've been building Rails applications for ~5 years and then met Ember.js last February. It was love at second sight (at first sight it went through a rough transition) and I've been mostly doing Ember since as a freelancer/consultant/trainer. I also started an Ember mailing list last August and have been creating content (screencasts and blog posts) to send to my loyal readers.
There has been an immense rise in popularity of front-end frameworks and for a good reason. User experience of web applications becomes ever more important and most user actions resulting in a full page reload increasingly seems like the 1990s although it is 2014. Matryoshka doll caching and sprinkling jQuery selectors is certainly a way to go but probably not the most maintainable one. Maybe, just maybe, we should no longer treat our browser (and our 2.4 Ghz MacBook Air running it) as an infant incapable of accomplishing any task on its own.
There is definitely more than one contestant for the front-end framework laurels, but the strong opinionated nature of Ember.js makes Rails programmers feel right at home. Rumor has it Ember.js initally has a steep learning curve so I'll do my best to give a first nudge on the journey to reach the summit, or at least a plateau.
I gave a very similar talk in Arrrrcamp (Gent, Belgium) last year, another one about Firebase+Ember.js in Osijek, Croatia and help a beginner Ember.js workshop in Eurucamp (Berlin).