I played Human Revolution from start to finish and it felt like a journey and a half - from Detroit, to Shanghai, to Montreal and the various facilities and complexes It was an awesome experience, especially going through and learning about all the characters, seeing how they all connect etcetera. I originally refused to play Mankind divided due to the whole 'augment your preorder' shenanigans, but I gave it a shot recently because no game really scratches an itch like a deus ex game does.
First thing I noticed right from the getgo was the lack thereof of references to the ending(s) of Human Revolution, the only point of reference being the incident that happens at the end of the game (if you've finished it, you know what I mean) and from what I can tell that's the only thing that led to the main overarching arc of the game (That being, the segregation of normal people and augmented people). To me, I'm not sure if this was a clumsy attempt at making a metaphor to racism or xenophobia- it was very blatant with shit like 'AUG LIVES MATTER' being spray painted on walls and such. Adam Jensen is one of my favorite characters to play, and it was in part due to his relationships with other characters in Human Revolution. Pritchard, Sarif among others- they make only small appearances or none at all in vanilla (Pritchard comes as DLC). This means that you're having to learn and get to know an entirely new cast, which I was open to.
The gameplay is solid, I had so much fun with the newer augments, and the more refined older ones. The stealth was even better, even if a tad easier due to the new way sightlines and enemy detection worked. I played it on the hardest (available) difficulty all the way through to the end and there was no section where I thought "there's no way outta this with my playstyle" which is great, Eidos deserve huge props for that.
I personally feel like a lot of the characters were wasted potential - Characters like Chikane and Aria felt like they could've had much more done with them. The twist involving the psycologist was one I liked, it's a shame that it was right at the end. Other than that, the only other characters who really stood out to me were all characters from the side missions - The mind controlling guy, the case involving the harvester and even the side mission involving another character from Human Revolution
Now, the characters aside - my main issue with the game was the setting. Having most of it take place in prague, made the game feel a tad 'samey' and it didn't feel so much like a journey. The snow facility, The aug holding place and London were great and designed really well. But there wasn't enough of that.
My biggest gripe with the game, and the thing that has given me the sour impression - is the ending. Not only did it break the series tradition of giving you a big choice at the end (Perhaps a good move to some), it was so open ended it feels like they ran out of budget or time or something half way through the game. I didn't play the DLCs, because I was put off by the vanilla games ending (Not to mention, I don't think any of the DLCs are set after it). It felt like half of a game. Hell, the fact there is only ONE BOSS FIGHT in the entire game, is a huge let down. A boss mind you, who I don't think was built up enough.
Overall, I had fun throughout my playthrough until I hit the ending.