So far the only place that I see reliable NFC payment is Starbuck. So there's very little use of it in the market. It's a matter of egg and chicken problem.
Maybe it'd be better if it just work when the phone is unlocked (i.e.: without starting another App).
Maybe there'd be a lot more place supporting it if it can just implement Visa PayWave as the default NFC payment method? So it has lots of shops supporting it in the beginning.
From what I gathered, Apple already has a huge number of major chains on board, so there's already a lot of shops supporting their stuff too.