I work with Andrew at Yipit. As he mentioned in a comment below, we're using features of Elasticsearch that aren't (and probably shouldn't be) exposed by haystack, and some of the query building started to get a little messy.

I'm excited Andrew decided to work on this during our last hackathon and that now we're able to share it with the community.

We've been really happy with Elasticsearch. Hopefully this library will help more people leverage Elasticsearch in their python projects.