Yesterday the Android 4.1 Jelly Bean update was available for download, but it was only for the Galaxy Nexus devices that were given away to attendees at Google I/O, which happens to be the takju GSM version. We knew the development community would be super fast and make it available to all and they delivered.
XDA developer bigxie posted the GSM version and all you have to do is download the ROM (below), wipe, and flash via ClockworkMod Recovery. He even posted a root fix with an updated radio that you can flash with ClockworkMOD.
Verizon owners get the experience as well thanks to DroidVicious at RootzWiki. Everything seems to be working and stable. Just download the ROM (below), make a nandroid backup, wipe data with factory reset, wipe cache partition, wipe dalvik cache (optional), flash the ROM, Flash SuperSU zip, and reboot.