I recently discovered an easy way to root the Galaxy Nexus. I just got my wife a GN and needed to root it so that she'd have decent battery life. While scanning posts I had used for my previous GN rooting, I noticed a new, "simple" approach which did not require unlocking the bootloader. As noted, the major caveat is that this only works with ICS 4.0.2 or earlier. Since my wife's phone came with 4.0.4, I decided to flash it back to 4.0.2 before proceeding. See the nexus factory images page and my post on flashing to stock. I used the 4.0.2 build (ICL53F). After flashing, I re-locked the bootloader by re-entering fastboot mode (power off, then hold VOLUME UP + VOLUME DOWN while pressing POWER until you feel the phone vibrate) and issuing
fastboot oem lock from my computer.
Once you are on 4.0.2, download the simple root package referenced at the bottom of the Android Forums post. Don't forget to turn on USB Debugging on your phone (under "Developer options" in Settings). Before running the root script, I checked that
adb was working properly by running
adb devices and observing a (16-digit hex) device id. See my original Nexus rooting post if you get nothing or lots of question marks. I found that rooting was as simple as running the
root-unroot-for-linux-osx.sh script that came with the "simple" package. Kudos to scary alien for making it so easy. Leave me a comment if it doesn't work for you---I'll try to help.