I have aluminum ones now that leave a rub on my boots and sometimes bang me in the shins when I carry it, but it's not a huge deal to me. I just have to be extra careful to make sure when I throw my fender over the seat, to make sure it is secure. I have been whacked in the face with a wooden stirrup and that hurt enough, I imagine an aluminum one would leave me with a broken nose.
I wish I knew someone with those Walls ones. They look interesting, but are rather pricey for my poor self.