The end result isn't an alternative with a 1% gain over cookies. The end result is a system that writes & reads to all possible data stores available simultaneously. The gain from that is a site where an "always logged in" can be potentially much, much longer.

There are still a large number of people who have terrible problems managing web site logins. Reducing the barriers to using your site for returning visitors is definitely a goal with a lot of value and clear ROI.