It's a cool video, and a cool airplane, but why should you care about Solar Impulse? According to this article, the answer is simple: "Solar Impulse’s flight across America could unlock the future potential of solar energy," as the "technologies aboard Solar Impulse could be used in the air as well as on the ground to power the next generation of clean technologies – greener cars, cleaner appliances and more energy-efficient buildings." Very exciting.
P.S. Also see this article about pilot Chip Yates, who "wants to repeat Charles Lindbergh’s historic flight across the Atlantic — in an electric airplane."