I tried the following on my new MacBook with Retina screen:

java Code:
ImageIcon i = new ImageIcon("/Users/joop/Desktop/picture.png");
JButton b = new JButton(i);
         b.setPreferredSize(new Dimension(57, 57));
         b.setMaximumSize(new Dimension(57, 57));

The picture is 96x96 pixels, because this works on WindowsXP
with a normal screen and a picture of 48x48 pixels.
I would expect that on Retina all graphics would shrink a factor 2.
Any ideas?