Take the following with a grain of salt ...
We started prototyping with ES & Rails about 2 days ago and I quickly discovered that things became a bit unwieldy the more I utilized elasticsearch. For now I am running with this type of integration with rails 3.2.15 to assess elasticsearch.
While we have done preliminary reviews on how to set up a production environment (still scratching my head on how to handle the split brain bug) , there's certainly plenty of what I'm not aware of, so if you see a fault in this approach, please let me know.
I may update this later on with a couple of convenience methods on the data models ...