Brian: I can personally attest to the fact that the graphing did work in the original release of the app; I suspect the release that was done to fix iOS 7 compatibility also was modified to support the iPad natively (instead of running it as an iPhone application) and that the graphing mode stopped working as an unintended side-effect.

I would bet that it’s an easy bug to fix (minimally, native support for the iPad could be disabled for the time being and it could go back to running as an iPhone app, which worked quite well) and that one way or another we’ll see it working again very soon.