Today is that day every Nexus owner has been waiting for since June 2014, after Google unveiled the next iteration of Android. Google has officially announced that it has started rolling out the latest Android 5.0 Lollipop update for most Nexus devices. The devices which are currently running on KitKat will be updated to Lollipop and the newly launched Nexus 6 and Nexus 9 gets a small bug fix update.
The Lollipop OTA update is rolling out for Nexus 5, Nexus 6, Nexus 7 WiFi (2012 and 2013), Nexus 9 and Nexus 10 devices. The OTA update for 3G / LTE versions of the Nexus 7 (2012 and 2013) have not yet started, nor have they started for the Nexus 4.
Note: As with most Android updates it will be rolled out in waves to users. This can take up to 3 weeks after availability for some devices has been announced. Please remember by pressing the 'Check Now' button multiple times a day in the System Updates section will not increase your chances of getting the update.
With the OTA update live, Google has also posted the full system images of the updates on the Google Developer site. The 5.0 images are available for the Nexus 5, Nexus 7 WiFi (2012 & 2013), Nexus 9 and Nexus 10 along with Nexus Player. No Nexus 6 image listed yet.
Those who are eager to get hands-on Android 5.0 Lollipop and can't wait for the OTA to arrive and the one who are using the Developer preview version of Android 5.0 Lollipop can / have to flash the factory image of Android 5.0 Lollipop. Make sure that the data will be lost.
You can download the image for the following devices below:
Head over to this page for instruction on how to flash the image files manually.