To date I have had no issues with it particularly as there is some substantive foam in the areas surrounding it. I have not noticed anything on mine which I have to say gets some serious usage but certainly hasn't scratched mine in any way. I am that happy with my iPad one that I have recently purchased similar crevasse Otterbox Defenders for my partner's new iPad mini and my iPhone 4!!!
Though well protected from bumps and scrapes by the military spec Griffin product I used on the phone, it was a nuisance if I wanted to use the camera .... having to uncover the lens and then try to get the cover to clip back while the camera was in use. Aesthetically too it wasn't a patch on my Otterbox ones being just jet black with the dimensions of a brick!!
Now I have a range which looks good, offers protection and allows pictures to be taken in an instant without missing the shot!!
Thanks. I actually put duck tape inside around the sharp edges of the circle.