I love this concept! The graphics are great and it's soooo nice to see some beautiful and uplifting natural scenery when so many other games have dark, blocky, depressing environments. The running companion that challenges you is a great idea too. Running feels natural and mostly works well except that it seems to lose tracking here and there. When that happens it slows down or even stops even though I am still running in place.
The biggest problem is the fact that you can't look around while running because the direction is based on where you look with the headset. It would be great to introduce a way to turn with the orientation of the controllers instead. Or with the thumbstick so that you can use this on a treadmill.
Once that is fixed, it would be great to see other environments/landscapes (beach, woods, mountain tops...). And then if there were things to do with the hands while running (shooting a bow for example), that would be awesome.