If you're getting tired of the default look and feel in either your NetBeans or Eclipse IDE, you might want to try out some skinning features. I stumbled across a skin for Eclipse, done through the Presentation API a while back, and have just recently become aware of the Substance Platform Look & Feel for NetBeans.
I've really got no problems with how Eclipse looks at present, but this plugin allows Eclipse to take on a Visual Studio theme. I can see this being particularly useful for developers moving from Visual Studio to Eclipse. In particular the Minimalist version of the plugin does a nice job of presenting the user interface:
You can get this plugin through the update manager using http://andrei.gmxhome.de/eclipse/
The Nebula project also provides a presentation based on shelves, but this is still in an alpha state:
On a related note, there is a plugin that allows you to run Eclipse in full screen mode, saving up your screen real estate for code editing.
The Eclipse wiki has more infomation on using the Presentation framework to customise the Eclipse RCP look and feel. There are also some code examples that illustrate the power of the API. As well as being able to modify the L&F of the IDE, you can use these plugins to give your own RCP applications a different look.
Developers using NetBeans as their IDE have opportunities to change their IDE too, using the NetBeans Substance Look and Feel Plugin. It's a pretty impressive plug-in, and gives you lots of predefined skins through the Tools/Options/Miscellaneous dialog.
This makes your NetBeans IDE feel like a new application:
I'm sure I've missed some other options to change how your IDE looks, so please let me know if you know of other plugins for NetBeans or Eclipse.