I started Bioshock Infinite yesterday and I must say, I'm thoroughly impressed. I love the atmosphere of Colombia, a lot more than Rapture. Its nice to not be confined to tunnels and dark rooms... I love having a bright sky and vibrant world to look at. The views are stunning, the church in the beginning and the ascent into Colombia were amazing. I'm still trying to find the sweetspot for the graphics configuration with my PC, makes me want to get a new GPU, not that I need one or anything.
The combat is fantastic, the shooting feels a lot more controlled than the other Bioshock games. I like the ranged combat, its a nice change from the relative close quarters fighting in Rapture, the Carbine is my new favorite weapon. The health/shield/salt system works well. And Elizabeth... I don't even know where to start about her. I love the fact that she doesn't simply follow you, instead she makes her own path or stays ahead of you, while you push her through the level. She leans on objects in the world and becomes completely immersed in it. I've never played a game with an AI partner that's integrated so well into the game.
Edit: I like the autosave system, it makes you focus on playing the game instead of making saves every time that you accomplish something.