When you buy a Nexus, you buy a lifetime subscription of Android updates just like when you buy an iPhone. Since Google uses these Nexus devices as platform and testing devices, updates for the same are always welcome and offered to all Nexus owners. All those who have held on to the Nexus 4 which was released in November 2014 will be happy to know that Google has a surprise for you. All Nexus 4 device owners are receiving the Android 5.1 Lollipop update over-the-air within few hours. It may take time so you can check for the update manually also.
The update is huge as it measures 174.5MB and is being rolled out to all Nexus 4 devices in batches. There are few improvements and enhancements such as the Quick Setting Menu. Bluetooth and Wi-Fi settings have been tweaked up here and there. From now on you will be able to easily manage notifications from system apps and others through the Interruptions option in the Priority profile settings which is cool indeed. I am amazed what Google has done within such a short span of time.
In terms of Security, the new Device Protection feature helps you track a stolen or misplaced device. Voice calls get With the HD Voice feature voice calls have become clearer.