I played this game over the weekend and thoroughly enjoyed the game play. There is a amount of decent difficulty to the game, if you are a low level you can simply go after higher level missions if you want it to be harder on yourself. For instance, if you are level 4 there are level 6 missions available. Honestly, I don't find the game to be jokingly easy. There are missions that could be more challenging, but with any game there will be easy missions and difficult missions. I have never bought an AC game for the multiplayer aspect; I have always bought it for the story and open world game play.
The game looks great and I haven't seen too many issues with glitches/bugs. One review mentioned the AI not reacting to fighting, but I haven't noticed that. If you walk up to a random AI and threaten to throw knives at it then it will run away in fear. One thing I have noticed, when you are next to a wall and need to quickly scale it then it may prove difficult. On the XBOX One you press RT+A to run and climb, but if you start too close to the wall then it won't do anything, I have to take a running start. I am talking about a wall, and not a house or building. I think that they have improved the free running so you're not constantly trying to climb everything you pass, and when you want to quickly descend it is a lot easier now. Also they have included a grappling hook type device which is a little bit odd to get used to but makes for quick climbing of tall buildings.
An amazing feature is the ability to drive carriages, it makes it so easy to get around the map! It is almost like Grand Theft Assassin lol. You can get into a horse-drawn carriage and drive it around the map. You can even knock over street lamps lol.
Overall I think it is an improvement over Unity, and I think over Black Flag as well. Everyone has just started to dislike AC games in part because of the bugs last year, and the fact that they gave a free game for those who bought the season pass. Honestly, Unity did have some bugs, but I really enjoyed the story and the bugs weren't so ridiculous that it took that much away from the game play. It has become popular to dislike AC titles rather than give them a try.