I noticed this nice writeup on the early experiences with the Beluga Skysails. It gives some real numbers, like a 10% reduction in fuel use for the ship, and a realistic report on how the highly risk averse maritime industry evaluates and reacts to a radically new technology. Kudos to the US Navy for supporting this effort with their long term contract to use the ship. They understand that it takes several years of genuine operational experience to settle in a technology. (At least in this case. The USN overall track record is a lot shakier.) A few more years and some higher fuel prices may see more of these ships be launched or retro-fitted. The retro-fit alternative is one thing that makes this technology interesting. It reduces the capital investments needed.
The cover page has a better picture. The photo in the article is some heavily photoshopped composite. I've seen the real ship carrying the real wind turbines, and it did not look like that at all. They did go for a symbolic use of a sail assisted ship carrying wind turbine on it's first commercial voyage. But it was only turbine blades above decks.