Dishonored is more Deus Ex than Thief
Dishonored is a game that does a lot of things right that a lot of games do wrong. Most noticeably, it is simply a joy to control your character. He seamlessly moves through the environment at all times - whether it be under or over obstacles that would block movement in most games - but in particular, the 'blink' power is a fantastic idea that solves the problem of imprecise jumping in FPS games, and allows you to traverse long distances with ease and haste, both vertically and horizantally.
The level design is such that spatial awareness is rewarded. What might be up there, or how about down there? Can I reach that place using blink? There is never any obvious path, even if you always have a particular objective (or several objectives) in each level (I highly recommend turning off objective markers, though, to better immersive yourself in the open-ended level design). Dishonored is much like the original Deus Ex in that regard, reflecting its game design philosophy, but it's executed with much smoother controls and some wonderfully potent abilities at your disposal that make navigating through the levels, and removing any human obstacle in your way, a breeze.
Much like Deus Ex, though, the AI and stealth mechanics are not exactly impressive. Don't mistake this for being a specialized stealth game like Thief, even though it is superficially more reminiscient of that series than Deus Ex. The stealth in Dishonored is purely based on cover blocking the enemy line of sight - light and darkness have no bearing on your visibility. And though it may seem ridiculous, you cannot be seen when leaning out of cover. But then this is not a game that aims for realism, but one that revels in fun game mechanics, and what the combination of steampunk technology and weird, wonderful magic powers has to offer the player in terms of choice.
Where Dishonored disappointed me is when it comes to the characters and the narrative. The game does not manage to involve you in this regard, with a predictable plot (that also ends rather abrubtly following a disappointing final level) and one-dimensional characters that are hard to care about, and rarely have anything interesting to say. Instead it is the beautiful world that Arkane has created that, as you explore it, opens itself up to your imagination, and thus a more fleshed out narrative world. Fragments of texts, bits of conversations that you overhear - any implications in things like that have a much greater impact on your involvement in the narrative world as you simply stumble upon them, and begin to fill in the blanks.
It is one of Dishonored's greatest strengths that the designers understand this dynamic so well - that player interaction and imagination is absolutely the best way to explore and flesh out the narrative world surrounding her, not through force-fed information. It's largely what made Deus Ex a classic, and Dishonored may prove to be one as well, given time. Right now, though, my feelings towards the game is such that while it's fantastic fun to actually play, and while it mirrors the ambitious design philosophy of Deus Ex, it lacks the quality writing that made the latter game a more interesting one to explore. Still, Dishonored is no doubt one of the year's best, and totally worth the price of admission if you like games that reward player curiosity and imagination.