The display looks beautiful! I just can't get over the black border... why, Apple? Why???
I REALLY like the border. It makes the iMac look MUCH more like it's just a display by reducing the perceived chin size as well as the distance from edge of screen to edge of the casing. A regular LCD might have 3/4" from edge of LCD to the outside edge of the case, and it was usually a dark color which helps improve contrast (see below). The old iMac had a lot of bright white space between the screen and the edge of the computer.
Black borders increase perceived visual contrast on the screen and 'improve' picture quality for the viewer.
For real. It's an eye thing.
What he said.