In terms of song selection, last I had heard, the pros are all allowed to select up to 100 different songs that they want to dance to. Of course nearly half are taken out since the show can't get permission to use them (which may explain why we're getting so many repeats of songs from seasons past). Edyta said she quit requesting songs, because the songs she requested went to other couples. So even if they request a certain song, it doesn't mean they'll get it. Derek could have asked for something 50s style, but got Rihanna instead. And no, they don't get their music right away.
If Nicole wasn't with Derek I'd be inclined to believe it might be a more even playing field. But because he's like King Midas to the judges, I just believe that they won't care when Nicole screws up, when she has lifts, if he has gimmicks in the dance, if the routines aren't any better 3 weeks into the competition. Her dance last night seemed awkward in the movements. She does take away what this show really was designed for-someone coming in and learning to dance, not a dancer learning to dance. Lil Kim wasn't always scoring as high with the public, which many believed is why the judges overscored her on dances. I doubt Nicole is any danger right now, but the scores could easily reflect that they're trying to balance the lack of votes they're getting.