I wish Sally Sparrow could have been the assistant this time round. It would have been perfect. She never even met the Doctor I don't think, so wouldn't be too much of an "old friend" as to draw attention from Matt Smith, but would be a familiar face to ease him in, rather than having two new completely new characters.
Plus Carey Milligan is gorgeous, and a great actress.
Plus it would bring a whole new dynamic to the weeping angels episode, as she has seen them before, maybe play in her fears, and nightmares of the first event.