Most of, at least my, customers still thinking in UI and forms. In their opinion building the UI, and not the business logic, requires the main effort. According to that tools like matisse are very dangerous, because even a Java beginner is able to build slick UIs in few hours. The UI looks good, but do not have any functionality. The problem here: your customer thinks, that your project is almost completed and wants to deploy the application in the next time....
So the challenge is here to make your UIs looking unfinished in the first iterations :-). With Swing it is not a big problem. You can very easily change the look and feel. In the first iterations you should use the napkin look and feel (you can use the following system property to change the Look And Feel without recompiling the application: -Dswing.defaultlaf=net.sourceforge.napkinlaf.NapkinLookAndFeel).
In the last iterations you could switch then to something like Substance.
Netbeans 6.0m2 is a Swing application in the early iterations, so with napkin it should look like these screenshots (1 or 2) :-).
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