Update... On a lark, I spent a coupl'a minutes the other night buffing my MacBook (also polycarbonate) with a relatively smooth-textured cotton handkerchief, and, lo and behold, the scratches in its top-case (the worst of which I'm pretty sure were inflicted by the Genius Bar) began smoothing out.
Note that this refers to surface scratches, as opposed to the dissolved finish that instigated this thread, but it is worth noting, all the same.
