Really misleading headline. The study wasn't about hammocks at all, just a normal bed that sways. Makes me think more of being on a boat. I haven't experienced the effect, but David Foster Wallace wrote about it: http://www.harpers.org/media/pdf/dfw/HarpersMagazine-1996-01... (Not going to give the page number of the sleep thing because I believe everyone should read the whole thing :)
I read a few pages, and it's absolutely shit. This guy has a terrible attitude. Why would I read 20some pages about some guy bitching about cruise ships?
EDIT: I've actually been on a cruise, so I can tell this is all just a bunch of (highly subjective) crap.