I went into this game expecting to absolutely hate it because of what everyone said, and because there was no ambient music. While I hated the fact that there was no ambient music (in the cities at least, frontier was fine without) I loved everything else about the game.
I played it a couple months after launch and it was such a nice surprise, perhaps it was because I had lowered expectations, but to this day I still enjoy it when I go back to it and it's up there in the top 3 of the series for me. Great protagonist, best one outside of Ezio, actually, the only good one outside of Ezio. The rest have been bland and boring. Decent story, great setting, dynamic weather, season changes, frontier was fantastic, great music, great multiplayer, great protagonist.
BF and Unity are actually my least favorites of the series and in my opinion, 3 was the last great AC.