I despise them. They make one fall to the allure of "easy" art, which just results in mindless repetitive art. BUT, I must say, some brushes are good for base shapes.
the only time i hate them is where they're all that are used to create an artwork. (yes, i used to use them excessively; i like to think i've seen the error of my ways since then. ) if someone uses a few here and there as accents, i don't have a problem with that.
With your style, its obvious no brush style is re-used.