I think the best use of language is the language that's appropriate for the character you're bringing to life and the story you're trying to tell. I think language should bring you closer into your character, using unique ways of describing things that fit in line with what that POV character is like. Case in point: The Scorpio Races isn't all flowery, purple prose. They are all just "regular" words. But the language is, nevertheless, delightful to read, because it so perfectly expresses what the characters are feeling, and lets the reader feel that, too. So if I were to focus on language, I'd focus on, as ecb once told me here on the boards, nouns and verbs. Finding the most specific ones for the scene and character. They might be poetic--but they might emphatically NOT be.
That said, sometimes the main thrust of the book is not the language, and you want to write invisibly, so you can showcase other elements and not distract from what the story is trying to be.