I see the point regarding curved screens, but I honestly see this as a simple question: Your head pivots essentially around a fixed point, at least horizontally, most of the time. So, I think having some curve in the monitor makes sense in terms of distance to the pivot point. That said, I think the curve radius would actually have to be a good deal more than they currently are to actually keep the screen surface at exactly the same distance all the way around the range you can turn your head (depending on how big and how close the screen is, of course).