Never in a million years would I have made that trade. Now, Ro and Forbes are both awesome, so if she had been on DS9 from the beginning it would have been fine. And the whole 'Ro was in Starfleet so the dynamic would have been different' could easily have been overcome with a simple uniform change. No problem.
But DS9 without Kira would be DS9 without its heart. She was the centre of that show from the very beginning, and I've always seen her as the main character, not Sisko. Visitor is an incredibly underrated actress too, and I think the show would have suffered a huge loss without her.
Plus, she's the only Star Trek cast member who's ever given me a kiss (and vice versa), so, y'know.