Penderecki is boss, but my 20th cent orchestral love remains with Messiaen.
I'm going to punch the first person who recommends Arcade Fire to me after watching Where The Wild Things Are.
Boulez himself has said that some of the stuff he recorded was basically stupid and useless (like Structures). Plus, like Bernstein, I like him more as a conductor than as the fantastic composer that he is.
You have to appreciate a forum where a discussion of a Twilight soundtrack leads to a discussion of modern concert music.