I've noticed that when my recently-acquired 15" MBP is on my lap, the bottom makes a clicking/creaking sound when the laptop is moved around, which is quite common when you're balancing it on your lap. (Yes, yes, it's not a "laptop" but a "notebook" but I still like being able to use it that way). My Late-2008 unibody didn't make a sound. I'm not sure if it is localized anywhere, because simply pressing on the bottom in various places doesn't cause any creaking. Is that normal with the sealed-bottom design?