The main goal is to demonstrate how to use various features of ember.js in a proper MVC way.
A secondary goal is to show some decent organization of files in the context of a Rails app. Reading through other blog posts i generally see excerpts of code presented in isolation, with little idea how they organized the overall app. Often, the file structure ends up being one big .js file and a big .html file with all the named handlebars views in it.
I have tried to structure my commits to lead the reader through step by step as they learn more about ember. I recommend cloning the repo, and then checking out each commit in order starting from the first. Understand it before advancing to the next commit. Use a tool like gitk to review diffs as you move forward, to guide you on which parts of the code to examine in your favorite editor to see them in full context.
Each commit along the way should represent a functioning app (with whatever limited functionality).
Each commit message tries to explain some points about ember, and highlight any potentially tricky issues. Sometimes in reading other people's code, you may notice something a little odd or different from how you have tried to do something, but not really understood why or how/whether it matters. I have tried to call attention to such things in this and be explicit about why they are there.