With a high-resolution ‘Retina’ display, it leaps ahead of rivals. Two years ago, Apple side-swiped the computer industry by releasing the first iPad. Though dismissed by some critics at the time as an overgrown iPhone, the iPad has proved to be just as disruptive to the PC industry as the iPhone was to mobile. And 55 million tablet sales later — including an incredible 15.4 million last quarter alone — there’s a new king of the tablet hill: the latest iPad.