A good subset of Pixel C buyers were likely to be waiting for this news with baited breath, so let's begin with a caveat before anybody rushes to the source link and kills their Pixel C's warranty with dreams of Paranoid Android and CM13; Nobody has managed to flash SuperSU or disable forced encryption under normal circumstances. There is, of course, cause for celebration. Just about a month after the tablet's release, XDA user cheep5k8 has managed to get TWRP, or TeamWin Recovery Project, up and running on Google's premium Pixel C tablet, albeit with a lot of help from TeamWin themselves. Mind you, as noted above, functions are limited at this stage; the /data partition where all the goodies are stored cannot be decrypted, so flashing just about anything will result in failure or perhaps even tears.
The working recovery, in its first revision, was only uploaded on January 8th, so the project is definitely still in its infancy. cheep5k8 is still working on getting everything going properly, however he has managed to get tethered SuperSU, meaning that the device cannot be allowed to boot without being hooked up to a computer and having the procedure, which involves some bootloader wizardry and fast hands, redone each time. The procedure also involves wiping your /data partition, which means a fresh setup on boot, as well as breaking all security settings. Setting a lock screen during the initial setup is not recommended. If, however, you are desperate to root your Pixel C and are willing to baby it and ensure it never reboots, this solution may suit you just fine.
A few caveats for the uninitiated, if you really want to go through with this as an early adopter. For starters, this procedure means your warranty is gone, no questions asked. You also may have issues receiving OTA updates and, as stated at the top, flashing just about anything under normal circumstances can result in failure and possibly tears. That said, if you want to be one of the first kids on your block with an unofficial recovery image on your Pixel C and watch the device's development scene evolve on your screen, head through the source link.