That's right folks, Google just began distributing Android 4.0 via OTA to GSM Nexus S handsets. Beginning today if your phone alerts you about an update there's a pretty good chance it will be Android 4.0, your pass to join Galaxy Nexus owners in an exclusive club of only two devices to have official versions of the OS :lol:
If you're too impatient to wait for the update prompt, it can be downloaded manually here. No details yet on how it runs, we're doing the manual download ourselves and plan to test it to destruction over the weekend.
While you're waiting on either download, it's worth checking out the updated Nexus S Help Pages, which have some tips on transitioning from Android 2.3 and how common actions have changed between versions.
Source: Android on Google+