I'm perfectly happy with their choice.
First, Jadzia was one of my least favourite characters and I think that Farrell was one of the weaker actors on the show, so not too sad to see them go.
Second, killing off one Dax host and introducing another one was great from the story standpoint, lots of cool things could be, and were, done with that.
And lastly, I am a fan of Ezri and DeBoer.
So, for me, this was win all around!