Android 5.0 Lollipop just started rolling out . Like all Android operating system releases, it'll probably take a week or two to filter down even to Nexus devices, and maybe a month or two before it starts showing up elsewhere. But in the meantime I've been using it on the Nexus 9 and Nexus 6 and the developer preview on my beat up Nexus 5. Not long enough to real soak it all in, but enough to have some general thoughts, the foremost of which is that Android Lollipop is great.