One sentence review: Tigana is a masterful work, a complex and character-driven epic. 
 What I liked: There is no element of carelessness to Kay's writing. His sentences seem carefully crafted, and his worlds are well thought-out. Important elements of the world are by and large explained (I can only think of one major example, and that would be the disproportionate strength of Brandin's sorcery), although exposition is kept to a minimum. The story rarely drags, and it is easy to get invested in the lives of the characters. Epics generally run the risk of being self-important or very dry, and Tigana does not fall into that trap. 
 What I liked somewhat less well: The ending. It wasn't specifically the elements of the ending that fell flat (although there was one storyline that resolved in a less than satisfying way), it was just that the ending seemed so...quick. The setup for the ending was so exquisitely done, a slow build. There was a real sense of the wider pain caused by Brandin's curse. But when the ending (final confrontation) came, it seemed oddly limited. 
 Things about which I am undecided: Dianora's storyline. Kay has done a similar thing since, of course, in Under Heaven. He's very good at allowing his stories not to wrap up neatly. However, since finishing the book, I have been stuck on Dianora. 
 In conclusion, Tigana is a book that has earned its reputation as classic epic fantasy. I highly recommend it, and feel free (in the comments now, or several months down the road) to tell me your own opinions on the ending!