For starters, it's worth noting that this isn't a new version of Minecraft; it has just been updated to work with the Oculus Rift. You can play in survival mode as well as join one of the many multiplayer servers out there. Once you start playing, you're presented with two different view modes. The first puts you in a virtual castle with the game running on what amounts to a TV screen in front of you. It's pretty meta and rather funny to be playing a game inside of a virtual reality game, but it's not a bad way to view things if you need a break from the full VR experience.
When you jump in to that full experience, the game shifts and you're completely immersed by what your character sees. Because of the massive scope of Minecraft's vast 3D landscapes, it really does feel like you've been transported away from reality, despite the humongous pixels and lack of fine detail. It's one of the best and more immersive VR experiences I've had thus far. In fact, that lack of fine detail actually helps Minecraft be so successful -- the game doesn't try to mimic reality. Instead, it felt more like I stepped into a cartoon.
The demo experience Microsoft was showing off goes through a few of the games signature moments -- I did some mining, fought some creeps, lit up some caves with torches, pressed a bunch of buttons to interact with the environment and eventually rode a mine cart way up the side of a huge building. That was probably the best part of the demo, as there was a real sense of speed and height as I rocketed skyward. A later mine cart ride let me look around in 360 degrees at the vast landscape from way on high as it headed towards a new area, and there was all sorts of activity and eye candy to take in on the trip.
As with most things VR, it's hard to do the experience justice in words, but I'll just say that the experience really highlighted the vastness of the world and did a great job of immersing me in Minecraft. It's a less radically different version of the game than the HoloLens experience, mostly because the Oculus version doesn't have gesture and voice commands, but it still seems like a great place to go exploring. Unfortunately, there's no word on exactly when Minecraft will be publicly available in VR, but hopefully it won't come terribly long after the Rift's release later this month -- "killer app" is a played-out term, but Minecraft has the potential to be one for the nascent VR scene.