> It looks like a helpful tool for situations where the standard colormaps in matplotlib/pyplot don't work well. Is that an appropriate use case?

Yes, that's definitely the type of use-case I had in mind. Another big one: Choropleth maps.

> I also like seeing nbviewer used for documentation, I haven't seen that very often.

Glad to hear it! It's my first attempt at writing documentation in an IPython notebook. Seemed like a good fit for something so visual.