OP, I'm concerned when you mention "smudges" that won't come off? ^^^ As suggested earlier, iKlear is the only thing that works for me. I spray iKlear on the microfiber cloth and wipe in a circular motion on the screen, then another spray on the cloth and wipe down the keys and the exterior of my MBA. Then I wipe it down with the polishing cloth and it looks pretty good in a matter of minutes. Those smudges concern me as you describe them, I'm wondering if you are keeping the foam insert between your screen and keyboard/trackpad as I do. This foam insert was with my MBA direct from the factory, and I've had a previous MB that developed smudges/scratches at the trackpad and spacebar that developed in about two weeks after my purchase. Well, whatever it is, keep us advised. Good luck. 😱