I shudder to imagine the experience of reading Infinite Jest in physical form. Having an ereader that could jump back-and-forth between the main text and the endnotes was invaluable.
Really? I first read it on a Kindle and it was totally infuriating. The jumping is not very convenient, certainly not anywhere near as fast as two bookmarks.
One thing about long books on e-readers is you don't have the psychological satisfaction of feeling like you're making it through the book (which you can feel by the number of pages that change hands with the paper book)
There's one footnote that ends up being a punchline, about five words long. The few seconds spent flipping from the page to the footnote lent it a certain comedic timing that would usually be impossible to portray in a book. That really stood out in my mind and I don't think it'd be quite the same by clicking a hyperlink.