I always liked the look of perforated cases. But they have issues. The holes let dirt in everywhere, which gets trapped inside the case, and over time the dirt will wear on the finish unless you regularly take it off, clean it out and wipe down the phone. If you don't, you get wear spots all over the phone in a perforated dot pattern.
Also, hair has a tendency to get into the holes. No one wants a case full of hairy holes. 😛