StavrosK has a hybrid auth system -- that's not a part of Persona (née BrowserID). Which is actually kind of cool -- because we use email addresses as identifiers, it's really easy to add Persona support alongside traditional auth mechanisms, and without giving up ownership of your users.
If you want to see a more "pure" Persona implementation, our standard example site is at http://123done.org/ (and you can preview the "Persona" redesign at http://dev.123done.org/).
As for as being as easy for first-time users as "Click here to log in with Google / Yahoo," well, we've got some tricks up our sleeves. Look for a blog post next month at http://identity.mozilla.com/ :)