I didn't care much for the main story. Although it was well written, it felt a bit... forced. And I didn't care much for most of the characters - either didn't like them or didn't care much. I liked Olgierd's brother, though, because that part with the wedding was great fun and Geralt got to behave completely out of character. Loved it. Having Shani back was nice but since I played HoS after the main story of the base game had been concluded, the option to romance Shani felt very forced. It would have been nice if Geralt could have told her "Look, I like you a lot but I'm with Yen/Triss now".
I have to admit that Iris and Olgierd's story didn't really touch me although it's a sad story. I didn't feel as torn when doing the Bloody Baron quest, though, because the von Everec story was pretty straight forward and the decisions weren't that hard to make. Also, the characters didn't feel as real as the Bloody Baron and Anna. I did like how the story was executed, though, and I think the painted world was pretty awesome. Nice gameplay there, and the bossfights at the von Everec estate were something else as well.
The Ophiri part felt rushed; at first I, too, thought that I had washed up on some distant shore only to find out that Novigrad was just around the corner. I expected something more to happen after I had beaten the Mage and the other Ophiri but nope. Just the runewright and the tradesman who ended up around Novigrad even before Geralt was dragged on that ship.
So to sum it up, I think HoS delivers some pretty awesome stuff, some of which is really dark, and O'Dim is a great villain. However, the story about Iris and Olgierd lacks something that makes me feel more sympathetic towards the two of them. As I said above, my main motivation for helping Olgierd was that I didn't want Gaunter to win, not Olgierd's charming personality or his sad story. I think that's my main problem with HoS: That I help a guy not because I feel he's been betrayed and that he deserves some happiness but because I don't want Evil to win.