Awful technical decisions such as: text justification and margins are fixed and inconsistent, spacing between words is awful, footnotes break the "navigate to last page" feature, pictures show up in the wrong place, tables look awful, charts and diagrams are full of jpeg compression artifacts) and so on.
It's really infuriating. Nowadays I check all 1-star and 2-star reviews for mention of "ebook" or "kindle". That usually keeps me from making a bad purchase. With the combination of lousy typesetting and comparatively high prices amazon really shows contempt for their customers.