I missed it. A Java 6 Release Candidate, build 60, was released November 10th. I've downloaded and installed it on both Windows XP and SuSE 10. I have, of course, started up my current NetBeans 5 Q-build under 6 on both platforms, and it performs quite well. The only complaint I have is the startup speed: NetBeans 5 10/31 Q-build starts slower under RC than it did under Beta.
The other big change, at least for Linux, is that the native Gtk support is much cleaner than I've seen for quite some time (see below).
As you can see, Java has clearly picked up the Gnome desktop theme I currently have. In the past the Java Gtk theme defaulted to some horrible grey-and-line-based look. This actually looks good for stock JFC client applications. Unfortunately, turning on the GTK style for NetBeans 5 still leaves a lot to be desired. Which is a shame, since NetBeans 5 on Windows XP has a beautiful theme that matches the Windows XP theme. What's more, sub-pixel anti-aliasing is now on by default, so the command-line switch required earlier is no longer needed.