The page preview thumbnails are so small you can't really make out details, and the size of the thumbnails or the sidebar can't be customized. That makes it hard enough to navigate a notebook if you don't have an outline structure in place as it is, then then changing pages when you're in a zoomed in view kicks you over to the selected page at the center of the destination page.

It gets annoying having to manually scroll up to verify the page title each time you move throughout the contents of a notebook.