Was lucky to get a 20min go on this yesturday at the Eurogamer Expo in London.
The game (well demo of the rooftop's) is vibrant, looks half decent however is very limited to what you can do or where you can go.
At first look's it seems to be an open-world, however it is similar to the old FPS's where there is only 1 path to follow and that's it, you start to lose any appreciation for something when you are forced through a certain path, with the same scripted events happening every time (especially with recent games giving you more and more open-worldness and unpredicatability).
The control's are simple, which isn't a bad thing, however you find yourself just running along spamming the same 2 buttons' all the time, need more input from the user to keep things fresh and even action-packed.
Overall, its not too bad, its somewhat unique, however I feel the simple control's and forced pathing lets the game down.