I like Ember over Backbone as it follows C over C which I found missing completely in Backbone. Though I feel that client side MVC have a serious case to use across all projects if file uploading and multi model support is seamless. File uploading hacks actually stops me from using it in major projects of mine.
Convention over configuration is fine until all you need is a little configuration, at which point it becomes a game of hunting down where the magic comes from and how to override it, because nobody thought that anybody would need anything other than the conventional approach, and so they didn't document how to configure it, and then your code turns into a bunch of workarounds.
