Firstly, I haven't been into webdev for a long time. I've been working on iOS for a little over 2 years now and given that prior, I found the semantics of ember.js to be a little more intuitive than angular.js.
At my current gig, I'm working on a vehicle fleet routing system, where my primary focus is essentially on getting the core algorithm right. I could have delegated to UI to someone else, who is better at these things than me. But eventually I had some free time and decided to do it on my own. Most of the UI is around a big Google Map, and given the limited time, I couldn't figure out how to write a wrapper view around it with Angular.js but with Ember it was fairly straightforward. It's very likely that I haven't explored Angular enough, but my primary focus here was to ship it to our internal users asap. Also, since I'd proudly told my boss that I don't need a front end guy, I had to get something working to save face. If Ember didn't work, I would've tried Backbone.js. BTW, like everyone else, I love the simplicity of Backbone.js.
Also, the ng-* attributes in angular templates feel a tad bit unpleasant. Handlebars templates OTOH, were very familiar. Probably because I'd used Mustache templates in an iOS project some time ago.
Actually, I found the documentation of Ember.js to be pretty good. There aren't enough examples around, but the documentation is pretty decent. Besides that, I learnt quite a bit of advanced undocumented APIs from Clemens Müller's blog (http://code418.com/).