The display of the PDF can be jiggered with, too. Page navigation is classy, too, with a Pages-style loupe which shows thumbnail previews as you slide your finger across the navigation-bar at the bottom of the screen.
Turn a page while zoomed in, for example, and the app respects the zoom level, but shifts up to the top of the next page, ready to read. These features are winners on their own, but the little details are what really make the app.