Does that depend on habituation? E.g., traveling in a car is often sickening until one's brain learns that the visual and motion sensing (inner ear?) messages are not a problem. For that matter, ice skaters learn to spin -- and apparently ignore the vestibular signals, if I remember the science special I saw where they were doing experiments in spinning chairs with such subjects. So perhaps someone who regularly layed down to exercise/sleep in such a framework would get used to it?

Which probably raises the issue of why one is laying in such a spinning framework? Perhaps to reduce the effects of prolonged zero-g?