Oftentimes it takes up to 5 minutes just for the transaction to begin, and usually more than 20 minutes for the transfer to complete.

I never understand this argument anyway. If you can't send funds instantly that isn't because the currently itself can't be transferred instantly - it's because for whatever reason you don't have access to a provider that will provide that service. That's a separate problem and can be solved without having to build an entirely new currency / financial system.