It tells an interesting story, and it's very,
very pretty. Probably the prettiest 360 game I've played. Character models are absolutely stunning, when Elizabeth displays any kind of emotion I feel empathy that I rarely feel for video game characters.
Combat is okay. It's better than combat in the other two games. I do like the Skyline addition, but no matter what people say, Skyline combat is oftentimes downright wonky and nowhere near as streamlined as people say it is. It's not horrible, but it could have been better implemented.
Hacking has been removed and replaced by the easymode Possession vigor. Sad

Several things seem like they're merely tacked on to the game, like melee executions. I tried those out a few times and past the mid point of the game they're worthless since you're usually crowded by baddies and will take too much damage if you get into melee range.
The vigors are cool and way more useful than plasmids ever were. CROW BOMBS HOOOO