Crossfilter was absolutely the inspiration. I just wanted to make a Crossfilter that worked with the arbitrary boolean composition, could be dynamically added to and updated, and supported some of the less numerical patterns I was encountering.

Coolies =).

Would you ever add some of the Crossfilter functionality, to make it easy for people to plug in their own data to PourOver?

I would absolutely like to add a Crossfilter Filter type. I'd even accept a pull request ... ;)