Just cooked up an EmberJS project and wanted to share some thoughts on the framework as a whole and also throw some gotchas.
1. Many things work out of the box. However, when you need to do something that is not out of the box, you will find few resources to help. Worse yet, things change so much that found resources may not.
2. Some things are shockingly easy to do. Some of those things include data validations, 2 way binding and active record (rails) integration with active model serializer.
3. Some things are shockingly hard to do. For instance, looking over a javascript object is pretty simple in javascript or jQuery. However, in ember (with handlebars) you have to convert it into an ARRAY first, then it will loop pretty easily. This surprised me because EmberJS is javascript… looping over and displaying JSON should be pretty easy.
If I had one recommendation, it is to not use templating languages or extensions like emblem. I used this during my first project. It is similar to slim or haml and makes it super easy to see how the markup will be. But the downside is that whenever you need to do something unique, you will fight with it in order to get it implemented.
Javascript frameworks look like they will be the way of the future so good luck if you get started!