So far, I tend not worry so much about perfect wording, breaking up long paragraphs, or anything like that. However, I do worry about making sure my story goes in the right direction. I got stuck on my second chapter all last week because I kept changing my mind about what would happen, eventually leading me to revise my entire plot (for the better.)
So, I guess First Draft is me telling the story to myself and seeing if the story itself is good.
Later drafts are there to make the actual telling of the story good.
Oh, and I do strive to use correct punctuation, spelling, and all that kind of stuff during the first draft. I just don't sweat things like "should I break up this paragraph?" or "is this an infodump?" I can always fix those later.