I don't know if this is just happening to me - I upgraded to Mountain Lion. when I open PDF documents in Safari, I use the single page scroll option, so that with a short scroll down the Magic Mouse, the page gets flipped straight to the next page.
Now, this worked perfectly fine with Lion, but in Mountain Lion, sometimes the page will wiggle a bit, but not actually flip over to the next page. This is annoying because there's no way way to tell if you've arrived at the PDFs final page - and because you loose time trying ten times just to flip to the next page.
Any advice here? Or is this just an annoying bug?