ember-data is a completely separate project that is still under heavy development. You can use ember without touching ember-data, and unless you are on the happy path of Rails with the active_model_serializers[0] gem, I would recommend not using ember-data.

You can roll your own light-weight layer, and Ember's object system will give you lots of rich functionality. There is also ember-resource[1] and ember-rest[2] if you want something a little less hand-crafted.

[0]: https://github.com/rails-api/active_model_serializers

[1]: https://github.com/zendesk/ember-resource

[2]: https://github.com/cerebris/ember-rest