I haven't "finished" finished this yet and I had been debating how to put together my summation of it in here so I decided to do it in two parts, first here where I only focus on the game itself and then later where I can do the full story and more about its place in gaming.
Basic things: Driving is dreadful. Maybe it's because I'm alternating this with GTAV but the cars, my god. I remember thinking that the steering could be summed up as having the car go in "directions" (ie forward, left or right) and that's pretty much it. Occasionally if you go round a corner quickly and violently enough you get what is probably supposed to be a slide, though all this does is highlight how bad the driving mechanics are. In addition, what is probably the worst vehicle/pedestrian AI since PS1 days makes it a far more stressful experience than it should be. Imagine the thought processes. "A car is driving towards me much faster than usual, with a siren blaring. I will immediately run out into the road in its path, then stop, then start to run back." Brilliant. Or the motorists, "I'm coming up to a junction and I can hear a siren, so I'll drive out then stop directly in front of a lane." Maybe they were going for a "cars are new so people don't know how to act around them" angle, but it's just so bad. Fortunately you can skip the driving parts, but being able to skip things which are bad isn't a good piece of game design.
Speaking of being able to skip things that are bad, something that doesn't seem to be balanced very well is the switching between the main gameplay mechanics of the interviewing/evidence hunting and virtually anything besides that. The driving is bad as I covered, the shooting segments aren't much better. There's no ammo counter, and although there's a range of weapons there doesn't seem to be much variation in their range/effectiveness. Aiming is annoying too. And juxtaposing these sections with the normal parts, it just seems off. Hand to hand combat sections amount to little more than fights from an NHL game. The same goes for virtually every on-foot section. There's what can best be described as a platforming section when you're climbing some scaffolding outside a building, it just seems to really not fit with anything else in the game. Especially annoying are bits where you have to walk along a plank or a narrow platform, where he goes far too slowly and is apparently unable to keep his balance. It just feels... off.
Still in the world of "off" and things which don't seem very consistent, I can't agree with Oscar above about the look of the game. The facial graphics are obviously brilliant and revolutionary, but everything else suffers. You watch a cutscene, you see a face with all its expressions and stuff, then the shot cuts to behind the speaker and you see the back of their neck and their hair and it looks like someone in the crowd from NHL 2007. The environments are similar in some sections, things like walking/running/jumping animations look really jerky and cartoony and while it's not game ruining and understandable, if they were to remake this in about ten years I think the whole thing could look much better. It's not really a complaint, just something you can't get past given the generation it was released in and the limitations of the hardware.
It's over three years since I first played this and I forgot how frustrating interviews and interrogations can be. Having truth/doubt/lie isn't much use when you don't know what sort of response Cole is going to have to that. It says to pick doubt if you think someone is telling the truth but has more information they can give you, but sometimes you pick doubt and he can be coaxing and get something out gently, then others he starts yelling and threatening them with jail and god knows what else. The piano noise from a wrong option is by far the most unenjoyable thing about the game, every time you hear it you know you've ****ed up and there's nothing you can do about it. One of the arson cases where it comes down to two guys you're interrogating, I knew full well which of them I should have been charging, but because I picked the wrong questions I couldn't. There's flaws in this style of gameplay, though I don't know what else they could have done to really get round it.
I think I'll leave that there before I start going into things that aren't strictly about the game and say, good game. Will hopefully remain important in making games something beyond pure escapism.