And if you are using Java and decide that you want to go ahead and use a full-blown widget toolkit for the UI outside of the map viewport, but don't like the look of the stock Swing look and feels, I have been (slowly) pecking at some (unfinished) extensions to some Swing widgets that let you just provide a bunch of PNG images to skin them, rather than having to putz around with the whole LAF subsystem.
It's.... somewhere in my mess of a svn repository. I could probably dig it up if you want it, as long as you send me back any improvements so I can use them later. XD
(scaled down from 1024x768, UI skin components from something off of opengameart.org)