I don't think there really is a jump factor... The dementors are semi static, and if they move, they aren't jumping at you... The film really warns you before you encounter the dragon, which moves but don't jump at you... It's really only a dragon's head moving around attempting to breath fire on you... That's really it... The intensity of the ride, in my opinion, is the movement of the vehicles on the track giving you the sense that you really are flying over the grounds of Hogwarts...