Ember 1.8.0 has been released.
Due to the Ember.Map changes, older versions on Ember Data are incompatible.
Is there any way to bring back compatibility?
f97d5c9adb contains a polyfill that fixes this, so if you can upgrade to this version of ED or later you’re all set. (I actually couldn’t figure out how to do this in ember-cli, would love some guidance here).
Otherwise you should be able to repurpose the polyfill for use within your app - although I’m not exactly sure how. The polyfill is here: https://github.com/emberjs/data/blob/master/packages/ember-data/lib/system/map.js.