Here's an iPad metric that you might not be looking at: Bible app sales.

Monday, a Bible cracked the top 10 highest-grossing book applications for the iPad for the first time, according to Drew Haninger, CEO of the scripture app's publisher, Olive Tree.

The theory of the case here is that if Bible applications continue creeping up the sales rankings, we can infer that the demographics of the iPad are broadening out from what we assume is an urban, liberal, fairly areligious base.