Just released - this is Steam's answer to the Oculus Asyncronous Timewarp, which keeps things smooth when framerate drops below 90 fps. I gave it a quick test last night in Serious Sam VR. The game ran smooth as silk - I even increased the video settings, whereas before I had microstutters in places and especially in the intro outer space scene.
It's only in SteamVR Beta, but so far so good. I will do some more testing this weekend with other games and see if I can get some super sampling in Onward (Quarantine1) without inducing judder as before.