If you have a yakju (check your model in /system/build.prop) model Galaxy Nexus, we have good news for you. You can now manually install Android 4.1.2 instead of having to wait for the OTA. You have to be on build JRO03C to install this new GZO54K build, but that’s it.
Even though this is an official build, be careful. Flashing any phone isn’t 100% safe. You know the deal, we aren’t responsible for any possible damages. Though we doubt anything could happen flashing official software.
Hit this download link for the build. Then hit up this thread for all the different methods of flashing this build. Choose the one you’re most comfortable with, since there are quite a few ways. Oh, the magic of the Nexus. Read carefully, flash safely!