The wife wanted the mirrored backcover on her iPhone 4S
The replacement went fast and smooth with the right tools. I forgot to order the iPhone 4S liberator kit initially and that is on my head ;-)
The screws are a right pain in the butt to remove unless you have the Pentalobe T1 screwdriver at hand. Don't attempt it without the right screwdriver. I replaced the old screws and at the same time bought a couple of extra Pentalobe screwdrivers from HongKong. The replacement was a breeze :-)
The original backcover was a bit difficult to remove after the two screws had been removed. It took a minute before I understood that I had to press the backcover another fraction more in the direction it was moving. When it was pushed *all* the way I could push it, the backcover was easy to remove. No further use of any tools was necessary before the new mirror backcover was in place and the two screws again had to be screwed in place.