I’ve already manually updated to Ice Cream Sandwich. Very snappy! Download the update here, copy into your Nexus S’ internal storage.
- Power off, then hold volume up and power to reboot to the bootloader.
- Using the volume key to navigate, select recovery, then use the power button to confirm
- When you see the warning triangle and arrow, hold the power button and tap volume up. You'll see a menu.
- From the menu, select "apply update from /sdcard", and choose update.zip from the list.
- Reboot and Enjoy!