I have a Nexus S for exactly this reason, and yet I had to wait well over 6 months to get ICS. It's embarrassing that they can't push out a new OS to their own phones on time.
I have a Nexus S (4G Sprint variant). I got the update to ICS a couple months back and the phone has become more and more unstable. The same thing seemed to happen with the updates my older HTC phone got as well. My experience with Android devices thus far can be summed up in 3 words:
