The Nimbus look and feel made it into OpenJDK6 yesterday:

http://hg.openjdk.java.net/jdk6/jdk6/jdk/rev/bdb2f5f4ac86

and I’m about to post a further slew of backported bug fixes for approval.

You can check out OpenJDK6 from Mercurial now and try it. You need to run the VM with the option -Dswing.defaultlaf=com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel. Refer to my previous blog on the subject for some example code.