Terrible glitches and bugs aside, this is a technically wonderful game that pushes the limits of live, thriving, and realistic environments. In saying 'realistic', I don't just mean visually realistic but also dynamic and behaviorally realistic. Crowds of people are noisy, bustling... chaotic; like they should be. Building colors and textures are random and work with the environment as being a natural 'part' of the environment. People movements (when they're not floating randomly sideways) - including Arno's - is as natural as I've seen in all the Creed games. We all know there was a tremendous amount of work put into this aspect of the game. The debate on releasing it too soon will be just that, a debate.
The game-play itself may have taken a back seat to developing the environment. It's not bad, it just seems to have stepped slightly backwards instead of advancing. Although the addition of the 'quick decent' action is a plus. But, when you loot bodies and it still says 'flour', 'wood', or 'oil' with a money value... why? As far as I can tell, you don't do anything with it anymore. Just give us the money! (By the way, I miss pick-pocketing.) I like having to unlock chests to get to the loot, but it should be a purchased skill, not a skill you gain by experience - IMHO.
But a disappointment in Unity is it's lack of adventure. Creed 1 and 2 stood out because you moved from location to location and discovered different activities and (beautiful) environments. Creed 4 did the same while on a ship. Being stuck in Rome, now in Paris (as beautiful as they are), lacks the adventure that moving to new locations presented. Included in that is the inability to leave the Animus. I don't care what others think, being able to 'get up and stretch' was an important part of the Assassin's Creed game-play. Now it's totally gone... I guess with Desmond out of the picture, Ubisoft can't justify that part of the game anymore? Losing Desmond, by the way, still sucks; as does losing the mystery of the First Civilization. And, giving us a piece of Eden at the end of the game that is broken? Lame.
However, there is one hope - a very enjoyable part of the game, and surprising: time-shifting. I'll forgo all aspects of leaving the Animus if time-shifting is explored more in-depth in future game versions. Either accidentally or purposefully, dropping into another time period while on a mission is very tantalizing proposition and opens up huge possibilities of game-play.
Without the adventure and without the mystery in the story-line, it was just a revenge driven plot. Kind of boring. But I did like the characters. And, having Arno be part of the Assassin's Creed society and not a stand-alone assassin was a plus to the story-line... even though something that happened between the group and Arno was never really cleared up at the end. And about the end, well, you would have a heart made of First Civilization-stone not to have feels.