While I enjoy the game, my problem is that the game gives you all of these fun, unique ways to kill your targets... and then slaps you and yells "YOU EVIL BASTARD!" if you use any of them. In Thief (a game that comes up a lot when I think of Dishonored), the nonlethal options were always emphasized, partially by the fact that you had nothing but some plain arrows and a gimpy sword to defend yourself with, but mainly by the game itself; you play as a Thief, not a killer. You're not there to kill some high ranking official or political enemy, you're there to take all the goods and money you can pocket and get out undetected.
In Dishonored, you're a highly trained assasin with mystical powers, and despite the fact that it's your freaking job to kill people, you're deducted points for doing it. Hell, the tagline of the game is "Revenge solves everything". It never says "Knocking people unconscious and stuffing them in a dumpster solves everything".
It's like handing someone a delicious carton of chocolate milk and saying "Drink up!", and as soon as they finish drinking it, you yell "WHAT THE HELL IS WRONG WITH YOU!?"