I'd like to start by saying that I am absolutely terrible at stealthy games, and (shame) I did have to play it on the easiest difficulty setting for it to be enjoyable for me. However, it was extremely enjoyable and it is a game that I will be playing and recommending to people for a long time.
The game starts out fairly quickly with about ten minutes of instruction for people who have never played. Right off the bat, you see how much this game relies on stealth. From my experience, this is not at all the kind of game where you can run around guns blazing and accomplish everything you need to. This was a big problem for me in the beginning of the game, because that's normally exactly what i would do in a game like this, but it simply doesn't work.
There is an option to play the game lethal or non lethal, and if you choose the latter, you are provided with more than enough tools to complete the game without killing anyone. On the flip side, you're also given a large variety of lethal weapons that will destroy nearly anyone coming your way, including police robots trained to gun you down with no mercy.
The thing I really enjoyed about this choice is that it was not concrete; if you chose to play non-lethal but you killed someone, you were not penalized for it. You just won't get the "Pacifist" achievement for not killing anyone (except the bosses, there's no choice there.)
Overall, an excellent and well put together game that challenged my mind as well as my skills as a gamer.
Conversation topic: Which ending did you choose?