The Android 4.1 Preview Jelly Bean OTA update for the Play Store version (takju) has been pulled and uploaded for other Galaxy Nexus owners to flash. Sadly, the OTA update will only work on the takju variant of the Galaxy Nexus running on Android 4.0.4 IMM076D.
Thankfully, a developer over at RootzWiki, b16, has managed to upload an Android 4.1 Jelly Bean nandroid zip file for rooted Gaalxy Nexus owners to restore back to. The zipped nandroid file is around 235MB in size and can be downloaded from here.
The nandroid file should work for all the different variants of the Galaxy Nexus without any issue. If you have root access on your Galaxy Nexus, unzip the download nandroid file on your phone, reboot into a custom recovery and use the restore option to restore the Android 4.1 Jelly Bean update.
If you own a CDMA/Verizon variant of the Galaxy Nexus, please do no try the above method. It might not work on your handset.
Update: A flashable zip file of Jelly Bean for the Galaxy Nexus is already available for download on ROM Manager. It can also be downloaded directly on your PC from here.