I don't like understated scores. I like loud pompous and over the top full tilt bombastic orchestration for each and every scene!
And even the slow scenes should be orchestral pieces that could almost stand alone...
Sonic Wallpaper Sucks.
Although a bit exaggerated, perhaps, Quasar makes a good point. I've been disappointed in many soundtracks where the music just becomes muzak. Lots of the early Doctor Who was like that, and many films have scores that are so dull it makes me wonder why they bother with a soundtrack.
Now I personally don't demand constant bombasticness (bombasticity?) in my movie/TV music. But there have been plenty of examples of excellent film scores where even incidental music has character and evokes the mood of the film. Ignore Celine Dion for a second and James Horner's score for Titanic is wonderful to listen to (even if it gives deja vu to us Enya fans). Star Trek TMP has bombastic passages, but it also gave us Ilia's Theme, which is still one of the most lovely bits of "quiet" film music ever written. Leia's Theme from Star Wars is much the same. And Murray Gold's "Girl in the Fireplace" theme from Doctor Who is the TV equivalent.
My favorite film and TV soundtracks are those you can listen to beginning to end over and over. Some of the early John Barry Bond soundtracks are like that. The soundtracks to the Prisoner definitely (though in that case much of the music was stock music). The new BSG has had some wonderful work, though I find McCreary's reimagining of All Along the Watchtower works better playing behind a scene than listened to standalone. And the 2 volumes of Twin Peaks soundtracks (vol 2 came out years after the first) are extremely successful in invoking the feeling of the original series. You don't even have to have ever seen the show.