I like how details fade around the edges -- though for maximum accuracy, there should only be a tiny area of high detail in the center, with most of the visual field being indistinct (as well as a total blind spot to one side). The brain just knows how to fill in remembered details of stuff you're not looking at directly, same way you tune out the sight of your own nose. Gaze-tracking and foveated rendering is a neat way of taking advantage of this quirk to speed up graphical processing:
I would argue that the viewer's eye already provides this effect. Whichever part of the image you focus on is sharp; the rest is indistinct. The result is that we are drawn into the scene better; we see as if our eye were allowed to roam around the scene as his was, rather than seeing the much more limited perspective with a fixed gaze.