Unable To Update to iOS 6.0
Unable to update iOS 6.0 software can occurred because of severals issues. Either Apples server are busy or bad network while you’re on OTA (Wireless Communication). Software Update Failed. An Error occurred downloading iOS 6.
You can try to update via iTunes. If this also fails your error says something like this: The iPhone “iPhone” could not be updated. An unknown error occured (6). More information: http://support.apple.com/kb/TS1275
If you’re using a jailbroken device, the only way to update, is to restore via iTunes. This cannot be done via OTA. Go to iTunes and “Restore” in your devices menu.
Here you’ll get the option to “Restore and update”. Good luck with iOS 6.