Codex Perductum

This company has a totally cool vision, trying to power ocean going vessels with enormous kites: KiteShip - Innovation in Tethered Flight

It seems totally cool. It would be environmentally friendly to a huge degree. Enormous sails could be made, the size of which sails could never match, but there do seem to be some drawbacks:

• Sailboats don't use wind the same way kites do. While they are some times pushed along by the wind, they also use wind the way an airplane wing does - especially when trying to make headway into the wind. So the kite could only take a ship in a direction that the current wind supported.
• What happens during a storm? Old-school sailors have perfected lots of methods for dealing with that sort of scenario
• Would a new hull design be required that maximizes efficiency when being pulled rather than pushed?