I was bummed about Jadzia leaving too, but gave Ezri a chance and loved her. Her growth over a single season was excellent, without hogging the camera and scripts (something they should have kept in mind for Seven).
I loved how the crew had to adapt to a new Dax, especially Sisko taking on the mentor role with her, and that Bashir actually got to get the girl in the very end (even if technically it wasn't the same girl). Plus we got to see a counsellor at work in the midst of a massive conflict, one who didn't have convenient empathic powers to rely on.
Also Nicole de Boer was a great actress for the role, who did a lot with the character in a short space of time and all without having to rely on skin-tight cat suits to get screen time