It's not as good as Thief or Thief 2, but it's a much more solid game than Bioshock or Deus Ex: HR as Battuta just said.
Unlike Deus Ex: HR there's no forced boss battles or real idiot ball moments for the player.
Like Thief, there's multiple ways of completing objectives.
Overall, this game feels a lot like what Bioshock 2 was trying to be namely with:
[spoilers]Emily reacting to your interactions with her and how you relate to the world.[/spoiler]
The game is very replayable, with lots of hidden missions, nooks and crannies, and different objectives or ways to execute missions.
There is some hand-holding, but not as bad as say Thief 3. Similarly what "quest compass" there is generally makes sense and is based on things like knowing the location of a room after being given instructions or blueprints. You can also turn off a lot of those sorts of things too.
Overall it doesn't feel like a dumbed-down game at all, probably the weakest part is that the AI is very standard Thief/Deus Ex style.
But... despite going ruthless kill-bot mode not necessarily being the best thing, stopping time and using it to nail dozens of guards is great.
Art direction wise the game is rather unique, and feels like a combination of Avatar: Legend of Korra and Half Life 2.