Mac Java - How to make a Java/Swing application look like a native Mac app

As I continue working on a text editor built for an audience of one (me) I've written a tutorial on how to make a Java/Swing application look like a native Mac OS X application.

My goal is to take this as far as I can, trying to make a complicated Java application look and feel like a Mac Cocoa application, but, I want to do this without severely compromising the cross-platform benefits of Java.

As I've mentioned before, I think Mac OS X is the best thing going right now, but if Ubuntu or some other Linux variant really takes off, I don't want to be tied to Objective-C code, I want to be able to port easily. Other people achieve this by writing web applications, but in this case I feel like I need more power in the GUI.