It is impressive, but it does show that the A7s's advantage lies mainly in the ISO levels that other cameras don't have, and when it comes to medium high ISO's, in the shadows of scenes. For "normal" ISO values, up to 6400 or so, there's very little or no difference, even in the shadows.
So if you never feel the need to go over ISO 6400, or if you do but you want your exposures to be "normal" (and not dark like a night scene), you might as well get the regular a7 or the a7r and have the option to use their resolution advantage.
Well, the a7s still has 4k video (to an external recorder) and the electronic shutter ofcourse...