I've enjoyed all the Assassin's Creed games to date but have never finished any of them, although I came close with the first game on Xbox 360.
The problem for me, as with many of Ubisoft's formulaic open word games, is that I get completely overwhelmed with a busy map full of icons and an endless mission log (and that's without any of the DLCs which just increase the bloat). I still get 30+ hours out of the game and until that point have a lot of fun exploring and taking in the story before I inevitably literally lose the plot and interest in playing further. There is a saying that you can have too much of a good thing and that is certainly true of Ubisoft's games.
As such, I am waiting on the reviews of Shadows before deciding whether to buy this for PC or not. I am hoping that this offers something unique to the franchise, like Origins did a few years back, and isn't just a remix of the recent Assassin's Creed games but just set in Japan. I am also hoping for a smaller more focused game like Mirage, which wasn't a bad game per se, just one that felt very derivative and unoriginal.