In our opinion, the passcode in iOS 7 has a visual security gap: when you enter your passcode, the larger buttons light up a lot longer than with iOS 6. It's always been possible to watch a person entering their passcode, but the new extended illumination, and increased button sizes make it much easier for the "viewers" to see exactly what has been entered.
Currently, it is not possible to turn off the extended illumination in the iOS settings. Our mobile device security subsidiary TOWER ONE has more information and explains how enterprise users of our TARMAC MDM solution can enforce a longer, harder to watch passcode. The highest iOS security level for passcodes is an unusual combination of at least 16 characters and four symbols.