Perhaps it's my software analyst bias talking, but for me the best announcement at Google I/O is Android 4.1, aka Jelly Bean, an incremental version of Android 4.0 Ice Cream Sandwich.
Google created Jelly Bean to unify Android tablets and smartphones, and after playing around with the update on both devices, I found no differences feature-wise. It also syncs more than apps. For instance, when you're consuming media on a Jelly Bean-ised tablet, whether it's reading a book or watching a TV show, you can start from where you left off on a Jelly Bean-ised smartphone. Suddenly, there's an incentive to own an Android smartphone and tablet.
Jelly Bean brings only a few improvements to Ice Cream Sandwich, but they're great. With auto-resizable widgets, uber-intelligent Google search, pinch-to-zoom notifications, and more shortcuts, Jelly Bean actually manages to make Ice Cream Sandwich look a little...bland.
Here at Google I/O we attendees aren't getting Jelly Bean-loaded devices for another four hours, but I got a demo of the update on a Nexus 7 tablet and Galaxy Nexus. Click through the slideshow below for a look at all the new features in Android 4.1, aka Jelly Bean.