It's not the case per se that is causing the scratches. It's dirt & grit that gets trapped in between the case and the phone that is causing the scratches. this is a problem with any of the silicone cases as they leave a little bit of room for small particles to get between the phone and case. The solution I found is to use the bestskins phone skin in combination with the incase sleeve. It works really well although not perfectly because the best skins leaves a little bit of the chrome exposed.
Also, it is best not to remove the skin for charing purposes, in other words dont use the dock. The more you take off the skin the more it deforms and leaves space for junk to get into the case and scratch the phone.
The silicone cases are good protection from drops. They do a good job of preventing dings and other nasty scratches from hard falls. Mine also keeps my iphone from slipping out of my pocket which is a nice side benefit. So I think they are still a good idea.
The chrome scratches easily..not a good design choice from a durability point of view but it sure does like nice when new 🙂