Ok, so played a few hours, here are my initial early thoughts. For clarity, in case anyone doesnt know, I adored AC Origins and AC Odyssey (both were my games of the year in their years), I preferred Odyssey over Origins, in part because I have long held a very deep interest in the classical civilization era so Odyssey was absolutely spot on for my immersion and relatable knowledge.
Graphics - I actually think there is too much happening with the graphics, it feels like they've crammed as much detail and things on screen as possible, the worlds of Origins and Odyssey feel less cluttered onscreen. I actually think they've tried to do too much with it and the engine is suffering as a result. There is quite a lot of variety in the graphics too, Origins and Odyssey were pretty much on a par within their gameworlds, their graphics were of a similar standard throughout, whereas in Valhalla so far I have seen some amazing looking things but also some pretty poor looking things, so there seems to be a much wider spectrum of quality compared to Origins/Odyssey. The animations do seem slightly glitchy at times, janky even in places. The landscape and draw distance is still as great as Origins/Odyssey and whilst you may not see too many people showing off unfiltered screenshots of characters you can bet your last pound that there will be many screenshots of the landscapes. I was also getting some screen tear, especially on the map for some reason. I think overall, from what I have seen so far (just Norway) , I'd put Valhallas graphics behind Origins and Odysseys (due to facial models and animations)
Sound - Suitably norse-esque really, I've heard some great tunes playing in the background and I look forward to hearing more, I will say though that there does seem to be some oddities with the speech, sometimes it sounds like the person is speaking in an echo chamber or into a tin can or something. Also, sometimes the walking/jumping sounds get suddenly too loud. A kind of audio jankiness to match the occassional graphical jankiness. Voice acting is hit and miss, some sound very good, others seem to sound more middle eastern or something, rather than scandanavian.
Story/Lore - I am liking the lore, I've found plenty of items to read and have found that the lore has been covered pretty well, I like the codex and the artwork and way its presented in there. Looking forward to further exploring where the story is going to go.
Gameplay - Right, first things first, the beginning is quite weak. Origins and Odyssey both grabbed me very quickly but I just didnt get that same feeling from the start of Valhalla, it wasnt clicking with me in terms of gameplay for the first 90mins or so, it was really only once I got to your hometown that it suddenly clicked into place. Not sure why that start feels so much weaker than the starts of Origins and Odyssey but it does. Maybe its because I am more familiar with Ancient Egypt and Greece than I am with with period in history, maybe its because of the janky items, not sure...but certainly once I got to the hometown it clicked. Talking of the hometown, I love the dice minigame, could see myself spending a lot of time playing that to get all the unlocks, I hope they add to it further over time and flesh it out even more. Another thing I really like is the new map/POI system, I think that the highlights on the map work far better than the old Ubisoft icon system. I do recommend putting the difficulty up, once I had pumped the difficulty up I found the combat far better than when it was on the defaults, made me have to think about what I was doing rather than just spamming. Regarding game size, I dont know how England compares in size with Norway but I've just done 3 hours of Norway and barely scratched it, so its going to be a pretty large game, I foresee myself getting 100 hours out of it reasonably comfortably.
Performance - Once I had dropped volumetric clouds , as per Origins and Odyssey in which I also had to drop volumetric clouds, I was able to hit a fairly steady 60fps in 1440 (1070ti) with most things set on Very High (or its equivalent), if I tried pushing stuff to Ultra then my fps dropped down into the 40s.
Bugs - I had no crashes in the 3 hours of play, I did encounter a few bugs though, my sfx disappeared for a little while after I had been looking in my inventory, once I initiated combat the sfx came back. I hid some clothing items so that they didnt display and then when I put my hood up and back down again, the clothing items reappeared and I had to go in and hide them again. I saw several "physics" related issues, things not moving as they should, bouncing off each other in a weird way or just objects interacting with each other in a weird way, one noticeable one was that my ship seemed to not move properly in the sea if I opted to row with sails down rather than use the sails. Dont know if this is a bug or just me doing something wrong, but try as I might, I could not get my character to dive into the water. Whenever I tried to jump into the water , off the boat or terrain, he just jumped in two footed all the time. Not the dive of Origins/Odyssey etc. Looked weird.
Overall - So, the caveat is that I'm only 3 hours in and very barely scratched the surface, only done a small part of Norway and the hometown, so long way to go yet and much to do and see before I can rate it properly, based solely on these 3 hours, I would give (what I've seen/played so far) Valhalla an 8/10 , I never give 10/10s but Origins and Odyssey were both 9s in my book, so based purely on this initial 3 hour start I'm saying Odyssey>Origins>Valhalla. However there is a lot yet to see in the game and I honestly dont think I will reach the best of the game until I get to England.