Jelly Bean isn't a huge evolution of Android like previous updates have been, but that's understandable given just how polished the OS has become. Still, as the company showed us on day 1 of I/O, things certainly have moved forward in quite a few ways (Ron provided a deeper look at some of them in his first Getting To Know Android 4.1 post).
Ah, the joys of owning a Nexus device. In what has to be some sort of record, Jelly Bean ROMs for the GSM and Verizon Galaxy Nexuses have been released and are ready to flash. And thanks to the Nexus being a dev device, getting the builds up and running is actually extremely simple.
For the GSM variant, just download the ROM, do a full wipe, and flash the ROM via Clockwork Mod Recovery.
It's kind of a tradition now for the Android team to create different boot animations for every Android release, and Jelly Bean is definitely no exception. Here's the boot animation from the Nexus 7 which is, as you all should know by now, the first device running Android 4.1:
If you need a refresher, here's the one from ICS, for comparison purposes (for science!):