I'm 150 hours or so into this and it's been great on the whole. It's a beautiful game graphically and I thought the 'mystery' markers were a really good way to handle side-quests. It represents enormous value if you're into AC games.
Not a big fan of some of the other side content, 'anomalies', 'orlog', 'cairns' and that fucking drinking game can die in a ditch.
Your trusty eagle (raven in this case) has been nerfed a little too much and isn't nearly as useful as it used to be. They're pretty much the only negatives I can point out, and, I still did all of the side stuff and collectibles (except that fucking drinking game).
I've hit some bad save issues though, lost a couple of hours of progress three times in total, despite being obsessive about manual saves after the first time. I got to a part of the game that really felt like the end, hit a glitch, had to reload and, bang, two hours or so of progress gone, the manual saves I made? Also gone.
Spat the dummy and will finish Medium, and maybe Legion, and wait for a patch or two before I go back to finish it off.
Despite that, I would highly recommend it to anyone sitting on the fence.