@krellin, I have used a kindle (briefly). And yes, I am obviously well aware that you can scroll with an ereader, and have done so.
My point is precisely that binary scrolling (forward or backward, at one or perhaps two speeds) is FAR less efficient and honed to humans' abilities than the incredibly fast process of flipping through a book. Let's compare.
Ereader: I'm at page 100 of an 800 page book. I want something toward the end. I open up a list of page numbers and scroll through it. The page opens, it's a little too late in the book. I open up the list again and scroll back... etc. etc. It works, but it's clunky.
Real book: I open the book to a late page, say 700, at a glance tell it's too late, quick flip back and I'm honed right in.
Basically in both cases you're doing a binary search algorithm, but the steps in the real book case are much faster at each step.
As for dictionary: I rarely actually use a dictionary while reading, but for those occasions when I do, I easily would prefer to grab the nearby dictionary -- which I have chosen because I like and respect it, not because it came on my ereader -- and flip with great speed to the word I want rather than typing it on screen.
For travel, again, it is of course more convenient to have it all on one ereader. I was referring to home.
Finally, yes, word search is one of the truly great features of an ereader that books lack. I wouldn't use it super often but I don't deny it's nice. For me it just doesn't make up for the many disadvantages, though.