Duo is an utter facepalm. What are they thinking. It doesn't make the device cheaper or lighter, in fact it makes it heavier and more expensive. It constrains your interaction and UI model. It introduces unnecessary mechanical complications and points of failure. It made sense for Nintendo on the DS because it did reduce costs and the device could be small and light enough for it to work. The Duo is just different for the sake of being different though. Classic solution in search of a problem.