UPDATE: Google has found some problems with this update. You can read more details in this article:
Google Delays Android OS 4.0 Upgrade for Samsung Nexus S
Google's Android OS 4.0 debuted recently on the Samsung Galaxy Nexus, but users of the previous Nexus model don't have to feel left out any more: an upgrade to the latest version of this operating system has started going out to the Samsung Nexus S.
This announcement was made on the official Android Google+ page: "We're rolling out Android 4.0, Ice Cream Sandwich, to GSM/UMTS Nexus S devices over the coming month, starting today."
As noted, the first devices getting this upgrade will be ones that can connect to GSM networks, including the versions offered by AT&T and T-Mobile. It's not clear when Sprint's version of this handset will get its upgrade.
It is being sent out "over the air", and users will be notified when it has been delivered to their device. This is happening in waves, so not everyone will be getting the latest version immediately.
Android OS 4.0 Preview
The latest version of this operating system was designed to re-unite the two previous editions. Android OS 2.x was created for smartphones, while OS 3.x was only for tablets. OS 4.0 will run on both, no matter the screen size.
It sports a number of changes, such as dropping the hardware buttons below the display that had been standard. These have been replaced with on-screen virtual buttons.
Many of the bundled apps have been improved as well. For example, the previous Contacts apps has been replaced with the People app. This includes not just address info and phone numbers but also has updates and images from social networking sites.
More about the Samsung Nexus S
The Nexus S debuted in December 2010 as the premier model with Android OS 2.3 (Gingerbread). It was the smartphone Google recommended third-party software developers use for most of this year, until the Galaxy Nexus launched.
It is built around a 1GHz Samsung processor, and sports a 4-inch WVGA (800 x 480), Super AM-OLED touchscreen which curves slightly to fit against the user's face. The device also has 3G (some versions have 4G), Wi-Fi b/g/n, Bluetooth 2.1, NFC, and A-GPS. Other features include a 5 megapixel rear-facing camera, a front-facing camera for video conferencing, 512MB of RAM and 16GB of internal storage, but no microSD memory card slot.