Update Moshi Keyboard Cover:
I thought I should make all aware of something I notice for the first time today on my rMPB (15"). I hadn't clean my screen in a while. I notice the imprint of the keyboard on the screen. The computer was in sleep mode and I happen to have the computer in an area where sunlight was shining directly onto it. The dark screen and the light made the imprint visible. After cleaning the screen there was no, I repeat no scratches.
I originally thought the Moshi Keyboard Cover did not come in contact with the screen. Now I have evidence that it does. No scratches however. I've had the Moshi cover now for about two months. I probably open and shut the case about 15 to 20 times a month. The computer rests primarily on my desk. I use it more as a desktop than portable.