This is great! I've implemented the PaymentRequest API on a couple of my apps, and customers have really liked the user experience on mobile chrome. This is another positive step towards PWAs becoming more ubiquitous (I strongly believe PWAs will play a bigger part in the app ecosystem in the near future). I can imagine Apple will feel a bit more comfortable with web apps if they could conduit payments via apple pay more seamlessly - I hope things like this help remove some of the dev inertia on their side and make safari more suited to web apps.