The official Android 4.1 Jelly Bean update has leaked, with the file being discovered waiting on Google's servers ahead of the official release next month. The Jelly Bean installer is seemingly the same file that is being pushed out to the free Galaxy Nexus handsets Google handed out to developers after the Google IO keynote yesterday.
Jelly Bean includes a new notifications system as well as Project Butter, Google's efforts on reducing lag in the interface. There's also a new Google Voice Search system to take on Apple's Siri, together with app encryption.
Meanwhile, Google Maps gets offline navigation, and there's offline voice dictation for US English. There's more on Jelly Bean in our IO wrap-up here.
You can download the Android 4.1 Jelly Bean update here [zip file] though be warned, it's unclear if all the bugs have been ironed out of this version. If you want the most stable release for your Galaxy Nexus it's probably safer to hold off until Google pushes it out OTA officially in mid-July.