First, it is about reading and comprehension. This site of Jakob Nielsen's includes these two statements:
"Low-resolution computer monitors make users read 25% more slowly from screens than from print..."
"High-resolution monitors with 300 dpi graphics exist and have the same readability as paper."
Next, it about visual information. I come to the Web from a background in painting, drawing and photography.
Finally, it is about pleasure and comfort, the kind that comes from good production values, from good taste and good craft.
Two stories about the IBM Roentgen display:
CNET
ABC