OK, so I just got back from the Apple store to see if my scrolling distortion problem is related to my video card (8600M GT - I have the early 2008 MBP). They performed the GPU tests and everything seemed to be in order. Which means that the wave-like distortion (horizontal lines) is software-related. I've heard that owners of the new MBPs have had the same problems, but are there any other pre-Oct 2008 MBP owners that are experiencing the same problem? It's not a big deal, but it's pretty annoying.