Jadzia never did much for me as a character. Farrell was very good to look at, but if that's all that I find interesting in a character, I'd rather see that character go.
I liked the character of Ezri, even though she wasn't a very original one. Young woman, struggling to find her place in life... Sure, they did an interesting take on it with the whole unwanted Joining, but other then that, characters like her are a dime a dozen. Still, I liked Ezri.
What pissed me off was the way they treated Ezri in the novels. She became a know-it-all bitch, constantly using the knowledge of the symbiont's prior hosts to proof that she 'rawks'. Constantly argueing with Bashir that she MUST be right in every fight they had, because not only was she a trained counseller, she also now had all this knowledge at her fingertips, so how could she be wrong? So you know what, she thinks, I should switch to command, since I can finally reach my/our fullest potential there. There were a few subtle hints that things may backfire, but in the end, Ezri gets command of a brand-spanking-new starship, since both the CO and XO died. I'm sorry, but she got a bit to much Mary Sue at the end. Here's hoping she'll grow into a more mature and stable character in the novels.