Running with a conservative estimate of the percent of Apple Pay users Bank of America (50M total banking customers) represents, Apple Pay enrollment rates in the U.S. would stand at 8%. If using aggressive metrics, Apple Pay enrollment would be 16%. I estimate 10-15% of iPhone 6 and 6 Plus owners in the U.S. have registered with Apple Pay.
It’s only been about three months since Apple Pay was released with iOS 8.1. I’m guessing some pretty gigantic usage numbers are coming with Apple’s Q1 2015 earnings release.