Then there's the menu system on it. Every DVD has to re-invent menus, usually badly. For example, they often do not display what options are actually set or not. Sometimes it's even hard to find the cursor.
The only good thing about DVDs is you can turn on the Eddie Mueller commentary for film noir movies. That man is an unending gold mine of snark, wit, and funny/interesting comments. He's often more interesting than the movie.