I've read the articles, watched the video on their site, and read the FAQ. It is unclear whether the app actually sends your card information to their servers. As I posted over on Hacker News:

No, Coin, I'm not going to store all of my credit and debit cards in a single spot on the Internet.

Your app has to work without Internet, or it's a security risk.

So... printed books cause eyestrain?

Or are you arguing that eInk screens cause less eyestrain than printed books?

I disagree. I've owned a Sony Reader and an iPad. The iPad is, hands down, easier on the eyes.

The Kindle and other eInk displays have a contrast ratio of 6:1 to 7:1. The iPad backlit IPS display is 750:1 to 930:1.

Other than perhaps directly under the sun, the iPad display wins. In dim light, the iPad owns.

Would you like another G1 to put in your drawer?

I realize there's always pain in being an early adopter, but Google and T-Mobile aren't being very kind to the owners of the original Android device. The phone is 17 months old and was last updated 8 months ago. That's even more distressing given that it (originally) could only be purchased within a 24-month contract.