Too lazy to download and install the brand new Android SDK yourself, don't feel like tweaking an AVD for optimal operation. Don't know what an AVD is. We don't blame you, and that's why we're here. We fired up Jelly Bean in the Android emulator and started poking around a bit. Sadly, most of the most exciting new features - offline speech recognition, Google Now - don't work. And we couldn't really delve deep into the new notifications system thanks to some limitations on the SDK. We could, however, play with the new version of Maps and demo the new widget placement tweaks. Most of the UI should look familiar.
Engadget , Android 4.1 SDK hands-on, Android 4.1 SDK hands-on