This product does work as advertised. Prolonged use (almost 1.7 years for me) and the clearguard is itself depositing gunk onto my keyboard.
I removed the clearguard one day to clean it, and apparently prolonged use of it wears off the plastic and molds it onto the macbooks natural keyboard. there are gloss (or oil?) marks on my keyboard now. it's also a little sticky. something i tried to avoid by purchasing this cover is here anyways.