Bom dia!
Estava procurando um Look and Feel e achei o Substance, que na verdade é um pacote com vários LaFs diferentes.
Encontrei nesse site: http://insubstantial.posterous.com/ e baixei nesse link: https://github.com/Insubstantial/insubstantial/downloads
Descompactei o zip, fui no NetBeans e adicionei todos os .jar em uma Biblioteca chamada Substance, e por fim importei no meu projeto.
s/s da biblioteca e do import:

s/s da chamado do método que define o LaF:

Mensagem de erro:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at org.pushingpixels.substance.internal.utils.SubstanceColorUtilities.getDefaultBackgroundColor(SubstanceColorUtilities.java:758)
at org.pushingpixels.substance.internal.utils.SubstanceColorUtilities.getBackgroundFillColor(SubstanceColorUtilities.java:661)
at org.pushingpixels.substance.internal.ui.SubstancePanelUI.__org__pushingpixels__substance__internal__ui__SubstancePanelUI__installDefaults(SubstancePanelUI.java:73)
at org.pushingpixels.substance.internal.ui.SubstancePanelUI.installDefaults(SubstancePanelUI.java)
at javax.swing.plaf.basic.BasicPanelUI.installUI(BasicPanelUI.java:56)
at org.pushingpixels.substance.internal.ui.SubstancePanelUI.__org__pushingpixels__substance__internal__ui__SubstancePanelUI__installUI(SubstancePanelUI.java)
at org.pushingpixels.substance.internal.ui.SubstancePanelUI.installUI(SubstancePanelUI.java)
at javax.swing.JComponent.setUI(JComponent.java:664)
at javax.swing.JPanel.setUI(JPanel.java:153)
at javax.swing.JPanel.updateUI(JPanel.java:126)
at javax.swing.JPanel.<init>(JPanel.java:86)
at javax.swing.JPanel.<init>(JPanel.java:109)
at javax.swing.JPanel.<init>(JPanel.java:117)
at javax.swing.JRootPane.createGlassPane(JRootPane.java:545)
at javax.swing.JRootPane.<init>(JRootPane.java:365)
at javax.swing.JFrame.createRootPane(JFrame.java:277)
at javax.swing.JFrame.frameInit(JFrame.java:258)
at javax.swing.JFrame.<init>(JFrame.java:181)
at JOB_Teste.Grafica.<init>(Grafica.java:21)
at JOB_Teste.Grafica$2.run(Grafica.java:87)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:705)
at java.awt.EventQueue.access$000(EventQueue.java:101)
at java.awt.EventQueue$3.run(EventQueue.java:666)
at java.awt.EventQueue$3.run(EventQueue.java:664)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:675)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
Procurei alguns tutoriais, o processo acima fiz seguindo o tutorial desse topic do proprio guj, porém ignorando a parte da instalação no NetBeans, pois queria testar o LaF antes de alterar o skin da IDE. Alguem de idéia do que possa estar acontecendo?
Obrigado e boa sexta-feira 
Testei com a JGoodies e funcionou, fiz exatamente a mesma coisa:
Será que é algum problema com a biblioteca que eu baixei?
Mesmo com a JGoodies, tentei aplicá-la em outros jframes e jdialogs que eu havia criado ha um tempo atras, porém apenas funcinou em um framezinho que tem 3 text fields, 3 labels e um botão, todos os outros lançam exception:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at com.jgoodies.looks.plastic.PlasticComboBoxUI.getMinimumSize(PlasticComboBoxUI.java:235)
at com.jgoodies.looks.plastic.PlasticComboBoxUI.getPreferredSize(PlasticComboBoxUI.java:260)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1660)
at javax.swing.GroupLayout$ComponentSpring.calculateNonlinkedPreferredSize(GroupLayout.java:3019)
at javax.swing.GroupLayout$ComponentSpring.calculateNonlinkedMinimumSize(GroupLayout.java:3005)
at javax.swing.GroupLayout$ComponentSpring.calculateMinimumSize(GroupLayout.java:2972)
at javax.swing.GroupLayout$Spring.getMinimumSize(GroupLayout.java:1336)
at javax.swing.GroupLayout$ComponentSpring.calculatePreferredSize(GroupLayout.java:2979)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1346)
at javax.swing.GroupLayout$ComponentSpring.getBaseline(GroupLayout.java:3073)
at javax.swing.GroupLayout$BaselineGroup.calculateBaselineAndResizeBehavior(GroupLayout.java:2732)
at javax.swing.GroupLayout$BaselineGroup.calculateSize(GroupLayout.java:2708)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1602)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1346)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1638)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1624)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1602)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1346)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1638)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1622)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1602)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1346)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1638)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1622)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1602)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1346)
at javax.swing.GroupLayout.calculateAutopadding(GroupLayout.java:1071)
at javax.swing.GroupLayout.prepare(GroupLayout.java:1059)
at javax.swing.GroupLayout.preferredLayoutSize(GroupLayout.java:878)
at java.awt.Container.preferredSize(Container.java:1788)
at java.awt.Container.getPreferredSize(Container.java:1773)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1662)
at javax.swing.GroupLayout$ComponentSpring.calculateNonlinkedPreferredSize(GroupLayout.java:3019)
at javax.swing.GroupLayout$ComponentSpring.calculateNonlinkedMinimumSize(GroupLayout.java:3005)
at javax.swing.GroupLayout$ComponentSpring.calculateMinimumSize(GroupLayout.java:2972)
at javax.swing.GroupLayout$Spring.getMinimumSize(GroupLayout.java:1336)
at javax.swing.GroupLayout$ComponentSpring.calculatePreferredSize(GroupLayout.java:2979)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1346)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1638)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1622)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1602)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1346)
at javax.swing.GroupLayout$Group.getSpringSize(GroupLayout.java:1638)
at javax.swing.GroupLayout$Group.calculateSize(GroupLayout.java:1622)
at javax.swing.GroupLayout$Group.calculatePreferredSize(GroupLayout.java:1602)
at javax.swing.GroupLayout$Spring.getPreferredSize(GroupLayout.java:1346)
at javax.swing.GroupLayout.preferredLayoutSize(GroupLayout.java:879)
at java.awt.Container.preferredSize(Container.java:1788)
at java.awt.Container.getPreferredSize(Container.java:1773)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1662)
at javax.swing.plaf.metal.MetalRootPaneUI$MetalRootLayout.preferredLayoutSize(MetalRootPaneUI.java:455)
at java.awt.Container.preferredSize(Container.java:1788)
at java.awt.Container.getPreferredSize(Container.java:1773)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1662)
at java.awt.BorderLayout.preferredLayoutSize(BorderLayout.java:719)
at java.awt.Container.preferredSize(Container.java:1788)
at java.awt.Container.getPreferredSize(Container.java:1773)
at java.awt.Window.pack(Window.java:808)
at job_hidrojato.Performance.BaixaServico.initComponents(BaixaServico.java:515)
at job_hidrojato.Performance.BaixaServico.<init>(BaixaServico.java:55)
at job_hidrojato.Performance.BaixaServico$6.run(BaixaServico.java:597)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:705)
at java.awt.EventQueue.access$000(EventQueue.java:101)
at java.awt.EventQueue$3.run(EventQueue.java:666)
at java.awt.EventQueue$3.run(EventQueue.java:664)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:675)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
Pensei ser alguma imcompatibilidade com componentes AWT, retirei todos de um dos frames, porém continua lançando a mesma exception.