The Vintage Space video Eleven Deaf Men Helped NASA Leave Earth describes a number of different NASA experiments done on human subjects who had damaged vestibular systems due to childhood illness.
The experiments described would have been a horrible experience for those with functioning semicircular canals (e.g. living in a room with spinning walls for eleven days, boat ride on choppy seas so bad most control subjects vomited) but the subjects were "completely immune to motion sickness".
During a crewed spaceflight mission from launch to landing, are there any useful functions served by the vestibular system? Do astronauts use this sense in any way? Does it have any redeeming qualities during a mission?