It's nothing like Thief though. Garrett is a wuss who can't fight his way out of a wet paper sack if you break stealth. Corvo (and Emily, especially) are the exact opposite of that and I constantly wondered why the fuck I was bothering to sneak around at all when I could just kill everything in sight with ease. I guess there's some challenge to be had if you can force yourself to play the game without killing anyone, but there's absolutely no way I could ever suspend disbelief on the idea that either of these characters wouldn't kill everyone who dared cross them. I do tend to "spare" the bosses though, as the outcomes there generally are of the "fate worse than death" variety.
Dishonored is a strange series. I very much want to like it, but I just don't. I could maybe get past the gameplay complaints but the chaos system is even worse, and Dishonored 2's version of it is just as bad as the original. In the end, the only things I really like about them are the art style and the setting.