I watched the Japanese and Taiwanese versions, but haven't watched past episode 3 of the Korean one. I like the Taiwanese version the most - it follows the manga fairly closely and the lead characters have wonderful chemistry, plus Zhi Shu isn't such a tsundere as he is in the other versions - and he clearly loves Xiang Qin. I especially loved the episode where he sees Xiang Qin wearing a bloody dress, and the final episode of They Kiss Again where he searches for her after she disappears. I think that Xiang Qin grew the most out of the three Kotokos (the Japanese name of the lead girl character).
The ending to the Japanese one was too rushed and I wanted to see more to the ending, but I agree that this lead was very annoying (especially with her big ears XD).