1) The combo box API docs say that the default renderer
   displays only strings. DefaultListCellRenderer actually knows
   how to display icons as well.

2) The docs say that if the model is not the "default" model
   that certain methods, like insertItemAt won't work.
   It should read that if the model is not an instance of
   MutableComboBoxModel...

3) The lead paragraph for combo box says that a combo box's
   editing capability can be disabled. This is misleading because
   the editing capability is off by default. So technically,
   this should say that it can be turned on.