I really liked Luna in the books, but also Ollivander--good choice of John Hurt for that initially minor role. I remember an article mentioning how they consulted with JK Rowling about casting and what may happen in the future books and thinking that, aside from the openness of top grade British actors to taking on minor roles (the Shakespearean tradition of ensemble troupes), it was a good indication that these peripheral characters would take on a slightly larger role later on.