The Jelly Bean (JRO03O) update that popped up on a Verizon Galaxy Nexus last night is now available for download. If you want to flash it though, there are a couple of things you should know. First, you need to make sure your stock G-Nex is running IMM76Q. Second, this is a test build and apparently not the official build that users will see. So if neither of those things bother you, then you should jump all over this.
It’s being reported that this JB build contains both a new bootloader and, wait for it, new radios (FF02 CDMA/FG02 LTE). That may make it worth it, right there.
The easiest way to do this, is to get yourself back to stock IMM76K. That may mean that you will need to flash factory images and wipe everything. From there, install ClockworkMod Recovery, download the IMM76Q file and flash it using “install zip from sd card.” After that, download the new Jelly Bean (JRO03O) file to your phone and flash it in CWM Recovery just like you did with IMM76Q. (This is a fantastic resource.)
Also, you could wait until someone turns this into a flashable .zip for any ROM.
Update: Radios from the update have been posted here.
Cheers El Madhatter, oldblue910, Jason and Manny!