I had two a-ha moments with it that sold me... There was a small demo room called something like Shopkeeper (think an old goblin's hut filled with wares) and I actually reached out to grab a faerie/wisp that was buzzing nearby. The second was a Valve demo app where a Portal like robot came stomping into the room and I actually jumped the F out of the way, only to have the floor start falling out from under me and scrambling back to safety.
For a few fleeting moments at a time there was no virtual, it was reality and it was freaking amazing. And all this without the added immersion the controllers provide.
The Vive is by far the best VR setup I've tried. It's made the rifts we had around seem like toys.