Smooth scrolling in Lion's Preview application sucks. Pressing the Page-Down key too quickly leaves you waiting for Preview to catch up to your position.
The only way I can find to turn this off is to switch from "Continuous Scroll" to "Single Page" view, but I don't want to view pages like that. The system prefs for "General/Smooth Scrolling" do nothing.
Is there any way to get my jerky scrolling back (apart from switching to Adobe Reader)?