Yeah, I don't care what other people do with their games. But for me personally, it would be a waste of money to do that. What struck me was how early this topic was made, the game isn't even out, so we don't know how hard it's going to be anyway - or what will be unlocked by doing XYZ. In DMC3, you only got crappy images for doing SS anyway.
I hope that in DMC4, you can't get rankings by using the extra powerful costumes. It shouldn't keep your score if you do it with extra powers like that, it defeats the point of ranking in the first place.