I've been known to make a few negative comments here and there about Sun's handling of Java recently, but I have to say they've really delivered on their Swing fidelity promises with the latest update.
The switch to using the native Windows font rasterizer for font rendering has made an enormous difference. It's just a pleasure to look at Swing applications now (and even though the Swing API is not perfect, I prefer it much more to SWT with its myriad of hard-coded SWT.* styles).
On the Linux front, the builds of OpenJDK 7 look really great on Ubuntu as well and have fixed most of the glaring GTK+ bugs.
Thank you Sun for a great job on this. It's good to see solid effort like this being put into maintaining Swing.
P.S. You asked for JDK 7 / GTK+ screenshots, so here they are:

