Netbeans GUI Designer
Have been using Netbeans for quite some time with out using it's GUI designer. My opinion is that Netbeans is better than many of the other IDEs I have had the opportunity to use. But there is certainly room for improvement. The GUI designer is one of them.
I was quite shocked to learn that the code generated by the Form Designer (as netbeans calls it) cannot be edited by hand. Obviously you can open the source in your text editor and make changes, but you cannot edit it from with in the IDE itself. That sounds like something you might find in an IDE by that Redmond corporation. The behaviour is most Unbecoming of an open source IDE.
The design that I chose to create was a Tabbed Pane. Suprise , suprise, you cannot change the names for the tabs!