Google has announced on their Android Google+ page that they have started rolling out Android 4.0.4 update for UMTS / GSM Nexus S (I9020), HSPA+ Galaxy Nexus (I9250) and Motorola Xoom Wi-Fi in select regions. Some users might receive the it for the first time, and others who are on Android 4.0.3 would receive it as an update that is around 17MB.
The Android 4.0.4 update brings stability improvements, better camera performance, smoother screen rotation, improved phone number recognition and more.
This update would be available to more devices globally in the coming weeks.
Thanks to @gauravh1 for the screenshot