I completed the story yesterday. Rather disappointed. It's a fantastic concept, and I have a good deal of fun profiling people (one I saw described as a 'clown fetishist') but the story is clich?d - you look for revenge for your niece's death. You have a whole city linked to this control system and they don't make enough of it for me.
The characters are not likeable enough for me to really care about. The niece is only seen in flashback so I don't feel enough passion to avenge her death as I saw so little of her. The only character I liked was Raymond 'T-Bone' Kenney, but you don't meet him until the second half of the game.
Missions are repetitive. There are, as you would expect from the developer of Assassins Creed, stealth missions. These are quite cool when you can stand outside a building and hack into the cameras and switch between them to complete a task without ever going inside yourself. When you get stuck on a mission though, you might find yourself going slightly mad before you manage to crack it.
The end of the game confirms there will be a second Watch Dogs, and that is a good thing because this is still an excellent concept which I feel they made a good attempt at but ultimately failed. I have no interest in playing the story again.
If you are thinking of buying it my advice would be to wait until it drops in price before doing so.