The Ember generators for yeoman are a bit out of whack. For now, I'd suggest you try out Ryan Florence's ember-tools (https://github.com/rpflorence/ember-tools), which can do many of the same code generation type things yeoman can do (we don't handle SASS/etc yet though; there is talk of generating ember-tools in with yeoman some day soon).
While Object.observe will be a welcome change, that basically means that your app can never be as performant as possible due to the design of the framework that you use for browsers that don't support Object.observe (dirty checking is NOT optimal). Using .get and .set so that all operations happen in a run loop seems like a small price to pay.
While I'm with you and love being able to write my own simple classes and POJOs, ultimately I'll value being able to support users who won't or can't upgrade their browsers.
I don't think this is so true. Angular's $resource has different goals and functionality than something like ember data. To me, Angular's $resource looks closer to Backbone's sync methods.
Things I don't see in Angular's $resource:
* Identity map
* Support for switching adapters (e.g. online/offline)