Google has just posted the updated factory images and OTA's for users to flash or sideload onto their smartphones and tablets. This is the April 2017 security update, and it's available for the Nexus 5X, Nexus 6, Nexus 6P, Nexus 9, Pixel and Pixel XL. Everything has Android 7.1.1 builds, but interestingly enough the Nexus 6 is also seeing some Android 7.0 builds available with the security patch. The Nexus 6 is seeing build N6F26Y for Android 7.1.1, along with builds NBD92F and NBD92G for Android 7.0. The Nexus 5X and Nexus 6P have build N4F26U, Nexus 9 with build N4F26X, and the Pixel and Pixel XL are getting build NOF27D.
At the time of writing this, the April 2017 security bulletin is not yet available but should be soon. So it's tough to say how important of an update this is, but this is a security patch, and they are all important to install on your device, so if you do wait for the OTA to come to your Nexus or Pixel device, be sure to install it, and not put it off. Since these updates are usually protecting you and your device from potential vulnerabilities, it's definitely a good idea to install the update.
You can also opt to flash the entire factory image, or sideload the OTA. Flashing the factory image does require you to basically factory reset your smartphone, so it's a bit more complicated than simply sideloading the OTA, and sideloading it is much faster. By sideloading it, you are leaving all of your data on your smartphone, so you won't need to worry about redownloading all of your apps, and setting everything back up the way you had it before. It's also a much smaller file, so the actual updating process is much faster. Since the OTA only updates the files that were changed, and leaves the others alone. We should be seeing manufacturers begin to push out the April 2017 security patch in the coming days. BlackBerry is usually one of the first to get things rolling. So it wouldn't be that surprising to see them roll out the update in the coming days for their handful of Android smartphones.