Google has started the dogfooding process of testing the Android 4.0 "Ice Cream Sandwich" update for the Nexus S, according to one of Google employees Adel Saoud. Dogfooding is a practice of having company employees use products before releasing them to the public ("eat your own dog food" in this sense apparently originated in Microsoft back in 1988), thus weeding out bugs while the products are still revolving in a relatively contained environment.
Just got Ice-cream Sandwich update on my Nexus S & it's looking great :)
Yeah an OTA, but it's an early one for Google employees so we test it further so it's even more awesome when you guys get it. So sadly I can't comment on it more at this time...
If all goes well, we'll hopefully see the official ICS over-the-air update in a few weeks (though in Google's case it might as well be a few months, if history is any indication).