I wanted to save, as a history record in my blog, the main reason that convinced me to go with the ember.js side instead of the angular. Here is the link ember.js vs angular.js and the article from quora which has some nice arguments from angular.js guys. Tom's arguments personally convinced me and the main thing that most similar angular vs ember comparisons have against ember is it's size (60kb gzipped and minified). But 60kb isn't so much of a deal in my opinion, an image alone can occupy this size, I find the performance to be much more important in most of my web apps that I develop and it seems like ember do it better. Regarding the regular changes, ember.js is in version 1-stable from September of 2013. Oh, is ember.js really faster right now from angular? here is a performance test (you can revise it if you disagree). Also, in ember are coming the htmlbars which seems pretty awesome, check this js performance and this slides.
My main problem of using an MVC js framework or not in general, has to do with the SEO and the general accessibility. If I want something simple which isn't so much of a web application, I hack my way through turbolinks and I try to keep it "old fashioned". If I wanted a super web application with a great single page feeling, I would go with ember. There are many seo friendly blog posts for mvc frameworks, which they are explaining how you can do it, but I feel like they need too much work and sometimes the result isn't the ideal (you have to run a headless browser and do some work on routing, but I feel like it is a hackish way).