I once experienced the most dissorienting situation in a Lear Jet when my handflying FO was descending at high altitude and while balancing fuel looked up at the instruments while in the clouds and saw my attitude indicator go through 30 degrees bank and increasing towards redline on airspeed. I felt level as obviously did the FO so it took every bit of discipline to take control and level the three attitude indicators to level flight. I was actually flying sitting leaned over in my seat because I didn't feel level. Experience got us through it, JFK JR didn't fare as well with vertigo. I don't think this would have happened with the captain in his seat even though he was rightfully taking his scheduled rest. I wonder how many hours each of the FO's had of actually flying an airliner without an autopilot in the clouds? My guess is 10 to 30 hrs. Airlines don't want you to handfly any more at a lot of places.