It's definitely important for really immersive VR experiences. I've not used the Vive or retail Rift but even on my Rift dev unit, tracking makes a huge differ

It's definitely important for really immersive VR experiences. I've not used the Vive or retail Rift but even on my Rift dev unit, tracking makes a huge difference in immersion versus just orientation tracking. I'd imagine that this is to be expected as it's a sort of "VR Lite" compared to more fully featured platforms. VR experiences will need to be designed with the limitations of the platform in mind and not rely on moving around in 3d space but rather focusing on head orientation.