The biggest change in Apple's new iPad is undoubtedly that Retina display. Cramming all those extra pixels into the same size screen is certainly a feat of engineering, but Apple didn't do it just because it can.
As anyone with a new iPad in front of them, or an iPhone 4/4S for that matter, will have to admit, having a Retina display makes the screen almost look like a magazine. It's impossible sharp, mesmerisingly clear.
According to one Optometrist and the editor of All About Vision, those extra pixels also help to reduce eye strain, too...