Google has just posted the factory images and OTA files for Android 7.1.1 for supported Nexus and Pixel devices. For those that might be wondering, the devices with files available currently are the Nexus 5X, Nexus 6P, Nexus 9 (and Nexus 9 LTE), Nexus Player, Pixel C, Pixel and Pixel XL. The update does also include the December 2016 security patch, so users will get both updates rolled into one OTA. Google has begun the OTA process, so you should be seeing the update to Android 7.1.1 hit your device soon. However, if you are impatient and want the update now, you can use the links below to grab the factory image or the OTA file.
The difference between a factory image and an OTA file is quite simple. The factory image is the full image of the operating system that runs on your device. Flashing the factory image means that you'll be wiping your device clean (which is often recommended when moving up to a new version of Android). While sideloading the OTA file is much easier. All of your data stays in tact, and it is only updating the files that were changed, so it's a much smaller update, which makes the whole process much faster.
For those wondering about the build numbers, the Nexus 5X, Nexus 6P, Nexus 9, and Nexus 9 LTE are getting NMF26F. The Nexus Player gets NMF26J, Pixel C gets NMF26H and finally the Pixel and Pixel XL get NMF26O. There's not a whole lot new in Android 7.1, for those that aren't using a Pixel or Pixel XL. The biggest change in Android 7.1.1 is perhaps the addition of the Daydream VR mode. So that other smartphones can take part in Daydream VR. The seamless system updates are also in this update to Android 7.1.1. Most of the other changes are under-the-hood changes, which will make for a better user experience. Sadly, the Google Assistant isn't in this update, as it is still exclusive to the Google Pixel and Pixel XL. However the rumor mill is stating that it'll be making its way on over to other Android devices in the near future.
Missing from the list of devices getting the update, is the Nexus 6. There's no word on whether it's being left out, or if it's just simply not ready yet. Given the fact that the Nexus 9 and Nexus Player (both of which launched with the Nexus 6) got updated, it's more than likely that the Nexus 6 will get Android 7.1.1 at some point.