Just fyi... Preview is a little bit wacky with inertial scrolling in the most recent upgrade of Lion (Developer Preview 3). When scrolling through a PDF, it starts to do page flip animations at "normal" two-finger scrolling speed. This makes the bottom half of each page unreadable, and it's really frustratingly poor performance. The good news is that you can turn off intertial scrolling and Preview becomes useable, if less smooth than it was under the first two developer previews. That's it. Carry on, citizens!