I've got one of the first C2D Macbook pros and I've noticed that (sometimes) when I move my hand across the palm rests that the aluminum feels ribbed and makes my hand vibrate. You need to apply light pressure and move your hands back and forth and you should feel it. Does anyone else's do this or am I just special? It feels pretty cool and you'll notice if it happens. On mine, it also happens over the speaker grates. Give it a try and let me know!