I've noticed that with themes, there generally isn't a constant look.
As an example, http://dev.jquery.com/view/trunk/plugins/ui/tests/modal.html
, Switching between dark and light, you notice that font-sizes and
padding/margin's change. Maybe this problem could be overcome by using
a common css file, and only change things by changing them in our
/* Rest of Theme's css.
Doing such would help in theme consistancy.
This is just my thoughts,