Played another 3 hours of this last night. Not sure if the performance has improved as I've moved to other areas, or if I've just gotten used to it, but it's not putting me off too much any more.
The game though, this thing is truly special. If you weren't a fan of the original I don't think there is going to be anything here to win you over, but for me this is really something else. The blend of player agency, satisfying stealth, and the beautiful presentation and world building is just ticking all my boxes. I love the wealth of options on how to tackle situations, and not simply in a very pre-defined approach as seen in the recent Deus Ex games where every challenge seems to have an obvious hack/stealth/combat approach laid out for the player. This is much more a case of giving the players some tools, setting up rules for how the world responds to them and then setting you loose on a variety of objectives, improvisation and experimentation is very much the key and has been very enjoyable thus far.
Sadly the plot and delivery of the main story looks like it's going to be a bit of a let down, as it was in the first game. It's a shame they haven't learned a lesson there. That's one of the reasons why despite everything the Dishonored series has going for it as a modern "immersive sim" it's still falling below the bar set by the likes of Thief, System Shock, and Deus Ex. Each of those earlier games set up the key elements of the genre (world and systems simulation, player agency, a great combination of ways to interact with the world and an encouragement to explore and experiment with how those could be used) but also married them to engaging and compelling (if slightly ridiculous and hammy in the case of Deus Ex) stories and characters. Thief in particular being a masterclass in how it delivers it's narrative through cut scenes, environmental storytelling, player interactions etc.
Either way unless it cocks it up massively as I move onward then I have to say it's pretty much locked on as my game of the year right now.