The Black Dalek is traditionally in a leadership role (think Vader) the gray and blue were the grunts of the Dalek world.
I wish we got to see these guys in action.
I fear the hunchbacks are going to be with us for some time.
I rather liked the Steampunk Dalek.
Like the Stone Dalek it should only be used when the story required it (like the undelivered promise of the Deco Dalek in the disappointing, Daleks In Manhattan).