Dishonored is a brilliant game, very challenging and totally different to anything else I've played (and I've played over 200 games on the 360!). Thus far I have only done a run-through where I killed pretty much everyone I that got in my way, and during that run-through I got the majority of the achievements that I could have done whilst playing in that manner (including all of those that are listed above that involve killing). I have to admit that I am dreading the more stealthy run-through as I thought the game was pretty difficult when I was allowed to kill (although I did play it through on the hardest difficulty and so will probably lower the difficulty for my second run-through). What I really like is the fact that even after having completed the game in one play style, the game encourages me to try another way, because I still have 20 achievements to aim for, unlike most games that usually award the vast majority of achievements during one play-through and then offer a paltry one or two if you complete the game a second time.
The only thing I didn't like about the game was the graphics, but get past that and the game is very rewarding.