They found a high correlation between interfaces judged as "beautiful" and interfaces judged as "usable."
The two researchers concluded that "it is suggested that the interface designers should strive not only to improve the inherent usability but also brush up the apparent usability or the aesthetic aspect of the interface."
Thanks guys, but we design die-hards knew this in our bones a long time ago.
In a freemium economy where customers see and try the interface before they buy, perceived usability is more relevant than ever. All else but aesthetics being equal, the better-looking interface will win out.
Compromise on aesthetics at your own risk.