The UI themes work great for all the controls they use but if you want to style a table or some custom html it gets tricky, sometimes you want the border of one class but background of another.
I would like to see themes with granular classes example classes below. This would allow the developer to style none jquery ui elements for more cohesive look.
ui-border: (whatever the default border color is for the theme, usually the one declared in .ui-widget-content)
ui-default-background
ui-hover-background
ui-header-border
ui-header-background