Nice, I enjoyed that
Couple of things though - in a couple of place (one of them very obvious) your viewpoint clips straight through a hanging vine. It just snaps you out of the moment when stuff like that happens.
At another point, my entire viewpoint clipped through a rock archway. I'm not sure if you're using the measurements from the Oculus Config Util, but if you are, you might want to actually set a fixed height for the viewpoint so those of us who are taller don't lose our heads
The only other thing is that some of the turns of the cart felt a bit sharp, and could do with smoothing out.
Overall though I liked it, and it's now on my list of demos to show people.