Preview at WWDC likely in June, followed by September launch.
Black iPhone 5 Anodized Aluminum Susceptible to Scratching?
One lengthy thread on our forums has been actively discussing the potential issue and Pocket-Lint in their review did note some wear around the edges after some early usage.
Ditching the glass back and reducing the thickness of the glass panel on the front has affected the design of the metal band around the edge of the iPhone. It is now chamfered and while that looks pretty, we've already noticed that on the black model the edge has started to wear, revealing the shiny silver aluminium metal underneath the "slate" coloured coating and, indeed, we've witnessed it on two separate models, ruling out a fluke manufacturing error.One person on another forum got straight to the matter and took keys and a SIM card tray pin to the back and edges of an in-store iPhone 5 unit with these results.
Of course, purposefully scratching a device is a bit extreme, but daily usage of any phone will generate some wear and tear. This may be a concern if you are particularly sensitive to the issue.