So far, it seems to me that persona is an incredibly useful technology in our space (Enterprise SAAS apps). Our space is populated by lots of apps that have various shitty login systems, but one thing they pretty much all have in common is an email address - and Persona seems to be a killer SSO system for securely leveraging/livening up these existing databases of email addresses.

Unless I'm missing the point, I don't see much alternative either. Just looking at the traffic from the Persona communit reinforces to me that I never want to be building my own authentication system - even if persona were to die as a project I would be better off cloning it than writing my own (or giving in and using social login, which is pretty undesirable in the enterprise world).