Earlier today (before the Android N deluge), we reported on the Nexus 5X update, which included a few important bug fixes. New there's a new build for the Nexus 6P that apparently offers the same improvements. It's build MHC19I, and it seems to have some noticeable performance improvements.
Here's the changelog provided by a Googler on Reddit. It's essentially the same as the Nexus 5X update.
General device performance
DND next alarm disappearing issue
Carrier-specific bug fixes
If you keep track of the various inside jokes of Android Police, you might be familiar with Artem's Luck. This is the principle that our illustrious founder will experience any and all bugs with devices and software because he has particularly bad luck. He's been seeing some serious performance issues with the Nexus 6P, but it looks like this update might have fixed them. That falls under the general performance item, possibly thanks to the addition of a user-space low memory killer. We're not sure about that, though.
Aside from that, there's a fix for the do-not-disturb bug that would break the "until next alarm" option every month, as well as some carrier improvements and tweaks. Presumably, it will also have the March security patches. You can grab the new system image from the dev site or just wait for the OTA to show up.