I bought it too. It's definitely worth $12. Code School is also planning a course on Ember.js to be released in the coming months. It will be a paid (subscription) course as well.

I did notice that Ember.js ran quite slow in my local environment. I'm curious if there's something I could do to speed it up in development. Having played around with Discourse, I'm certain speed isn't a problem in production.

I bought it. It was definitely worth the money.

Seconded.

Definitley worth the money but for my taste a bit too basic

Bought it, and yes it worth the money and is a bit too basic. I think they are planning to do a sequel with more advanced topics, especially regarding ember data.