I unboxed my new 13" Air yesterday and noticed something odd with the lid. It doesn't close flush against the body. The front edge (by the trackpad) is flush and the back edge is flush, but the sides have a gap. Almost as if the curved slightly. The gap is large enough that the side can be squeezed and you can hear the lid touching the body. The gap seems to be uniform on each side, so I thought maybe it wasn't a defect, but maybe designed that way. So what do you think, is this normal? At this point I could easily swap it out for another.