From: Michael Ross <michael e ross gmail com>
I am probably extending your last question outside the UML universe and you
intention...
"where (if at all) do you need to use shapes outside the UML set? "
I do all my work outside the UML set, and the beauty of Dia is its
flexibility at a low level. I always need shapes outside the UML set. My
dia tend towards illustrations for documentation of equipment and its use,
sometimes to get a particular presentation of graphs. None of it
specialized so that I am dependent on the sheets of shapes, but I pick
among many of the, in particular the electrical, circuit, chemical
engineering (a very handy set which I misuse regularly), assorted and flow
charts sheets. I often place images in Dia and annotate extensively on top
of them.
Dia is a very nice general purpose tool.