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.
The Bible, of course, is a mainstay iPhone book application, and easily the most popular book in the history of the world. On the Kindle, which probably has the broadest range of eReader users, the Bible ranked 50 in their list of best-sellers at the time of publication.
Olive Tree's NIV Bible BibleReader is the highest-grossing iPhone Bible app right now, too, ranked second in books just behind Green Eggs and Ham. Between the iPhone and iPad, including free versions, Haninger said his company is getting 3,000 downloads a day. The iBible may not exactly be iBeer in its heyday, but sales on the iPad are growing, Haninger said, as the device has passed 3.5 million units sold. (Atlantic colleague Eleanor Barkhorn also pointed out to me that the NIV is considered to be the more "conservative" Bible translation and less likely to be used at more liberal mainline churches.)