Wow, you are right: it DOES look a lot better with a theme. I had placed theming as a low priority item so I wasn't worry about the horrible look without any theme. Thanks.
I'm constructing a scrolling list with this
Panel panel = new Panel( 150, 150, true );
panel.setBackground( new Color4f( 1, 1, 1, 0.5f ) );
List< Label > list = new List< Label >( 150, 150 );
and it was sized correctly without a theme; however, the items in the list now display to the bottom of the screen even though the scrollbar is working.