Mine is clean as a whistle, then again I only use my iPad at home, and I make sure my hands are clean. 🙂
But like any light colored accessory it will get dirty if not properly maintained. I went with White cause Charcoal looked like junk. I really wish Apple would have released more Smart Cover colors for this. :/
I also recommend using some soft water on microfiber cloths for cleaning, alcohol and other cleaning products are something I only use for cleaning my windows. 😉
Kallum.