VR does not affect shutter speed. Think of it as a gyroscope that tries to keep the camera steady.
It's designed to manage minor handshake or, if you have an "active" setting, some bouncing if your in a car or other moving object.
Because the camera's electronics must process what is going on, you shouldn't use VR at shutter speeds of 1/500 or greater (some would say 1/1000) because the VR gizmo takes longer to settle.
Finally, VR should be turned off on most lenses when used on a tripod because the "gyro" will be continuously looking for movement. But read you lens manual on this because some later systems have made this rule unnecessary.