A great game all round, and much better on PS4 than on PS3. The next gen graphics make a world of difference, and make gameplay truly immersive. The story lines and characters are very engaging, but what truly sets this game apart is just how massive it is. There is so much content and so much to do in the open world of Chicago.
A couple of small criticisms about the game: Firstly, driving is quite challenging. Each vehicle handles and drives very differently, which is great from a game realism point of view, but it does make driving very challenging in game, and in my opinion, too challenging. Driving becomes a skill you have to master if you want to successfully evade enemies. Furthermore, you need to learn the subtle differences between driving, say, a sports car and a performance car. Each handles differently and each has it's own stengths and weaknesses. While this adds another layer of strategy to the game, it does make the game a bit more difficult. In my opinion, the game could be improved by making driving a little easier.
Secondly, I believe the game could make better use of the "reputation" bar when it comes to hacking. When you profile the general public, you get little snippets of information such as "Volunteers at soup kitchen" and "Participates in human trafficking". Yet there is no consequence to hacking and stealing money from either person, i.e. both are treated equally in terms of consequence. I believe that you should have a consequence in the form of a reduction in reputation for hacking people who do good (soup kitchen volunteer) and an increase in reputation if you hack people who do bad (human trafficker). I guess this may raise some issues around what the developers class and good and bad, and some people may be annoyed by an "enforced morality" but I think it seems a bit weird to be able to hack obvioulsy good people in the game, and have it treated the same way as obviously bad people.
Aside from those two aspects, the game is amazing and is definitely one of the highlights of Ubisoft's gaming stabel. I have yet too finish it, but I am really looking forward to the sequel. Like the first Assassin's Creed, I think it can only get better from here.