Cash on the internet. I want to be able to send money to someone else on the internet without trusting a third party, and I want it to settle quickly / in a way that is "cash-like" (no reversibility). It isn't going to solve all problems, but as far as I know there is no other global payment system that solves for what I described.
Sure, that's a good use-case though rather niche, as most people definitely don't want irreversible transactions. It's certainly well suited to that use and I agree better than normal payment networks for it.
I'm not convinced that niche in any way justifies the current valuation or hype, in particular from corps like Payal.
