the borders of internal windows were just one pixel thick, so it was very hard to e.g. resize a view or attribute table window.
With this update you should see the difference immediately. The broader window borders apply to all resizable internal windows in gvSIG CE (views, maps, attribute tables, etc.).
The updated Plastic XP theme has much wider borders and uses a thin black outline, which makes it easier to tell apart the contents of overlapping data windows.