There is some good news for the owners of Galaxy Nexus that you can now manually update to Android 4.1.2 Jelly Bean version. Those who are running “takju” iteration of the handsets can now update manually without waiting for OTA.
Android 4.1 Jelly Bean is the fastest and smoothest version of Android. Android 4.1.2 Jelly Bean brings updated Android Beam, Google Now, Camera, Notifications, System Enhancements, Accessibility and Google Play. Google Now a Siri Like voice assistant and enhanced search tool.Improved browser performance with updated java script engine (v8). Browser has been updated with HTML 5 better support.
To update galaxy nexus to android 4.1.2 you will need a Flashed Galaxy Nexus running takju firmware also ensure that your devices are rooted / bootloader unlocked and Clockwork Mod Recovery Flashed.
Step 1: First Navigate through Settings > About > System Update to check if you got OTA Update. If not then continue following the steps.
Step 2: Download the required file from Google.
Step 3: Transfer the .zip file you downloaded above to /sdcard (root directory).
Step 4: Reboot into ClockworkMod Recovery.
Step 5: Take a nandroid backup.
Step 6: Select install zip from sdcard > choose zip from sdcard > Downloaded in Step 2.