Comment 4 for bug 229112

I think the request in the new description makes a lot of sense (though it probably would have been better as a new bug report).

The user should be able to change the default look and feel be editing something in /etc. There are already a number of java properties files in /etc/java-6-sun that allow manipulation of other configuration settings.

As a work-around, I created /etc/java-6-sun/swing.properties with the swing.defaultlaf setting, and symlinked it to /usr/lib/jvm/java-6-sun-1.6.0.06/jre/lib. For anyone getting here via Google, the correct value for Nimbus is:
com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel
(beware though, it can cause Null Pointer Exceptions, see http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6800801)