I've come to a point where I'm really, really split on ACU now... and it has nothing to do with technical performance issues at all (that's seemingly all anyone else was complaining about).
My biggest problem with it is that the freerunning is really wonky now... when playing the other games in the series, I've never had this many screwups. The main problem is the whole "freerun up/freerun down" button system. It's just unnecessary, and barely works half the time anyway. It should be as simple as the "freerun up" button making you leap toward the highest point possible, while the "freerun down" button should cause you to descend toward the ground, while only pressing the standard freerun button ought to make you go straight... but it just isn't as precise as that. I tried playing one of the hardest co-op missions by myself, and there was a part where you have to run an obstacle course to collect flags. And while I realize it was supposed to be played with another person, it's also obviously meant to be doable solo. And I could have done it, except that the parkour is so fucking loose and imprecise. Tried a bunch of times, and Arno did nothing but jump to places I didn't intend over, and over, and over again. Demolished all fun I was having with the game, just with that little part. Now I can't play any other parts of the game without noticing all the flaws in it.
I also kind of hate that the combat has been changed the way it has. It may have been easier in earlier games, but it could still be intense if you really got surrounded, and the main point is that it was still fun . But now they've eliminated counter kills, taken away the bullet-avoiding human shield ability, and pretty much sapped most of the fun out of it. They mainly mean for it to be stealth now, obviously, but the combat shouldn't suffer because of that. It seems easy at first, but later in the game, much like the parkour, it just gets to a point of being frustrating. Guys keep pulling out guns and shooting you, and you barely have a chance to do anything because the only way to avoid bullets is to roll, which you'll be trying to do while others are slashing at you, which means you'll inevitably be getting hit no matter what you do. Not to mention that the controls become a bit unresponsive every now and then, and the enemies sometime attack without showing a counter signal, which will obviously get you killed.
And don't even get me started on how silly the aiming system is. It should have been as simple as using the same style of aiming you have in shooters like Watch_Dogs, but instead it's more like the stiff mess they had in ACIII... couldn't even tell you why they chose something like that. Cover-taking is unresponsive and aiming is a chore. Shouldn't be like that.
And it's weird, because even with all these issues, I still really want to give the game credit where credit is due, because there's a lot about it that's fucking fantastic. I mentioned before how immersive it all is, how good the graphics really do look sometimes, how lively the city of Paris is, and how fun the missions can occasionally be when you're given some freedom. There are a lot of places where I'm just in awe at how much passion the devs had for making something new and fresh for the series. Even though the gameplay isn't as great as it should be, it still shows that they were really, really trying to make something compelling and new, and I can't help but be impressed by the obvious effort put in here. But sometimes so much of it just seems a bit needless, and I find myself wishing Arno controlled more like Shay or Ezio or Edward.
Like I said, very split on the whole thing. Still haven't quite finished it, and after the smooth-controlling wonderland that was Watch_Dogs, I'm having a hard time going back to it. But I may force myself soon, especially since the free "Dead Kings" DLC is out now which might add some extra fun to it.
I just really hope they iron all these issues out for Victory next year, because the Victorian England setting is just too good for them to waste by using these exact same systems again. Changes need to be made, even if it means making it feel more like the last-gen games in the series.