I'd love to see somebody write up a higher-level description of what the user experience is like, what communication happens underneath, and what new pieces of infrastructure need to get built to make it all work.

A use-case to start with:

A customer starts with eleven on-chain bitcoin. They want to pay for a nice cup of tea. Walk me through what happens before/during/after the transaction, assuming I have a  lightning-enabled wallet on my iPhone and the tea shop has a lightning-enabled cash register.