Android Ice Cream Sandwich Features
android.com
android.com
The general refinement of the Android UX is by far the most impressive feature of 4.0. Face Unlock is just a lame, poorly thought out gimmick IMO.
Of course, they are aware of this. When you enable it, a warning is shown saying that the lock can be bypassed by using a picture or even with a person that looks like you! :)
Most people I know don't use a pattern, pin or password. If you're doing it for a security reason, then face unlock is just silly.
(For what it's worth, it would be much easier to grab a complete stranger's phone and get the pattern unlocked than the face unlock. The finger marks for the screen unlocks are incredibly easy to see)
You know what the antithesis of good mobile development is? Piling on gimmicky features just because. IMO, Face Unlock is indicative of everything that is still wrong with the direction of Android, which is such a shame because overall Android 4.0 is indicative that they are trying to shake that image by focusing more on the core experience.
In Firefox it improves, but it's still weird: http://i.imgur.com/c606f.png