Simulator sickness is different from motion sickness. That is, there may be low simulator sickness, but it turns out that pulling 9G turns or rocket jumping while running backwards at 40MPH, while not a problem on regular computer screens will get most people motion sick in real life, and hence in VR.
From personal experience and in watching a number of people in my office try out the DK1, I can definitely confirm that there are a number of things that are quite different when strapping on the Rift - relative scale of objects becomes much more important, world detail (books in bookshelves etc) takes on a much more interesting quality, and movement speed is definitely something that seems to scale down - feeling comfortable moving at walking/realistic speeds vs getting sick at traditional video game character speeds.
From personal experience and in watching a number of people in my office try out the DK1, I can definitely confirm that there are a number of things that are quite different when strapping on the Rift - relative scale of objects becomes much more important, world detail (books in bookshelves etc) takes on a much more interesting quality, and movement speed is definitely something that seems to scale down - feeling comfortable moving at walking/realistic speeds vs getting sick at traditional video game character speeds.