I Played Through Dishonored And I Do Not Regret It.
The world is alive. Everything you do has an effect. Not just on you, but the entire town. The more people you kill, the more rats there are, the more hostile the environment, and the more action oriented the game is.
If you want to play it as a stealth game (which I recommend), the game takes much longer (but it is worth mentioning that it is a rather short campaign, no matter how careful you are) and is much more immersive. It can also be quite stressful!
The game is easy to get involved with, easy to learn, and easy to become addicted to. It is one of the few games that I would play through again for the single player campaign.
On the bad side, however, the loading times are terrible. Every time you die (or start over because you effed something up) you have to wait for what feels like an eternity. There are also some points in the plot that are pretty predictable.
Over all, though, it is a great game. The multiple endings make it worth a second (or fourth) play through. I would definitely recommend it.