Using both cardboard and gearVR (with oculus s/w disabled) to view panos works really well.
However (and especially if a scene has a lot of detail) when you pan around there is a degree of juddering or jumping, some of my clients are saying this makes them feel giddy.
This is less apparent if the same pano is viewed as a 360 image within gear VR using the bundled occulus 360 image viewer so I am assuming its a function of the browser and VR implementation.
I am going to try 'downgrading' the image quality to see if this makes a difference, but would welcome others findings and comments.
cheers
Tim