I didn't like Kira for most of the first season. She was too hard and brusque, and it seemed like that was all that she was. Then "Duet" aired, and all of her character's potential, positive and negative, became clear. She's now one of my favorite characters. Kira's struggle over seven seasons to become better than who she was at the beginning of the show is one reason why DS9 is so terrific. I think "Duet" opened the door to that.