As a user, once your browser and email provider support it, it's single-click login (and signup), without any redirects. As a site operator, you don't need to

As a user, once your browser and email provider support it, it's single-click login (and signup), without any redirects. As a site operator, you don't need to choose which company you're going to accept as an auth provider, or have a login page with lots of icons on it; you just have one button that says "Log in".