There is actually as it was described on several product review sites: The shell is extremely sensitive to dirt and is also active with more careful treatment after only a very short time shabby and scruffy. The material used seems downright having hydrophilic properties and sucks all forms of contaminants into itself. To prevent this, you would need a protective cover for the protective cover, which indeed can not be the intention.
On a positive note the precise fit and the elegant manner of attachment with brackets. In black, the envelope is likely to recommend, in orange (and probably green) but not.