We knew Android 4.0.4 updates were coming soon, and now we know exactly when they'll start arriving: today. Google has announced that the latest version of Ice Cream Sandwich has begun rolling out to the UMTS / GSM Nexus S, the HSPA+ variant of the Galaxy Nexus, and the Wi-Fi Motorola Xoom. The update is said to include better camera performance, smoother screen rotation, and overall stability enhancements. Electronista reports that the some users are already receiving the update on their Nexus S devices, with AndroidPolice detailing a way for anxious Nexus S owners to install the update manually (though this method requires your Nexus S be on Android 4.0.3 already). There's unfortunately no word yet on when the updates for the Verizon Galaxy Nexus or the Nexus S 4G will be officially making their way to users.
Update: Google has now posted the factory images matching the Nexus S and Galaxy Nexus OTA updates.