I enjoyed Hearts of Stone more than the main game. There was a lot more dialogoue, which I really liked. I do wish the parts with Shani had lasted longer though. On that note, some people on the team obviously had a lot of fun with that "scene" on the boat.
Talk about risqué. I guess they took the criticism that all the previous scenes were basically the same to heart.
Hearts of Stone just adds to my opinion that the game needs an Enhanced Edition, Not only to rebalance everything once the other expansion is complete, but I'd like cutscenes at the end of the main game about what happens to Shani and Olgierd, for example. Hearts of Stone gave me that bittersweet feeling that the rest of the game didn't. The quality does dip a bit in some areas, and I still don't like the over-reliance on the Witcher sense mechanic, but I got that 'witcher" feeling 100% throughout this expansion, just like in TW1 and TW2.
I wish the rest of the main game was of this standard. It's so good, I need more messed up Slavic folklore! I'm still miffed about the Academy though. CDPR obviously put effort into designing it, but you're only there for 5 minutes. I think closing the Academy because of the war was a mistake. So many interesting quests could have taken place there.
After you finished that quest in the Academy, Shani tells you to come see her before she leaves. I looked in the Journal, and there wasn't any information about that, so I went and dealt with O'Dimm first, but then when I went back to Oxenfurt, Shani was gone. Is there any unique dialogue if you go straight back there after you deal with the professor, or is it just the same lines about how she and Geralt can't work. EDIT: Read through this thread, Shani is gone in my game. Maybe that's a bug. And from what I gathered, there's no other dialogue about the end of the quest.
Also, O'Dimm is a better antagonist that the Wild Hunt. CDPR seriously missed the mark with them.