I like her, too. It does seem like the writers didn't usually know what to do with her, and I think Farrell succeeded very well in some episodes but not as much in others. But I really liked her as a character.
I thought her scenes with Kira brought out the best in the character, and in Farrell's performance. Their scenes in "The Siege" are really wonderful. Jadzia was adorably grumpy without being bitchy, played the "Old Man" card without it feeling forced, displayed her competence as a Starfleet officer as well as her lighthearted feminine side ("what do you think of the nose?"). I wish more episodes managed to make her personality shine so much.