My 18-200 VR has two switches - on and off, and Normal/Active. In Normal mode, you can pan with a runner or racing car, and it only restricts vertical motion. Active restrains movement in both the vertical and horizontal axes, so it is best for still shots.
In either mode when shooting off a tripod with VR on, it will hunt. At low shutter speeds, this can introduce blur and at any shutter speed, you may get a different framing than what you expect. The latter will create problems if you are planning on layering the exposures for HDR, or when shooting sequences for time encapsulation. Each layer may need to be manually aligned.