I just finished viewing the entire DS9. Gul Dukat was by far one of my favorite characters and his evloution throughout the series was interesting. It seemed in the beginning he was more of a, for a lack of a better term, ally to Sisko when they consulted him about issues with the spacestation and such. I was happy to see him gain a larger role and how he seemed to portray some likable qualities (such as his genuine love for his daughter) but then he once again devolved into the scheming tyrant that he truly was by the end of the series.
I think with Winn, more so than any other character, we were able to see Dukat's manipulative abilities at work. Granted of course she didn't know who he was since he was a "Bajoran" at the time, but once she discovered his true identity it was too late for Winn, she was already corrupted.
Overall, I liked Dukat alot. I liked all of the Cardassian characters actually. I think their race was well protrayed throughout the series.