I honestly can't comment on whether or not it scratches the iphone, but it seems to protect it pretty well with not much area to get dust in and scratch it. I've also had the case for a limited period of time and really have no reason to take it off and inspect the phone.
I wouldn't know though, my Capsule Rebel was sagging and loose and scratched the phone up, so I'm not really that concerned about it. More just want a case so it looks cool and can take a drop or two.