Here's my rule of thumb that hasn't failed me yet. I do all movies in Movie Only mode, 6 ch sound, no subtitles.
The exceptions are:
1. Movies that fit on one disk without compression and
2. Episode DVDs because I need the menu to choose an episode.
Personally I don't like all the extras, especially how they do the special effects. It ruins the illusion. For example, when I learned clams and cow intestines were used in Alien, all I see now are clams and cow.