(Spoilers!) Twisted Infinity is a Lot of Fun!
Gameplay
The gameplay is joyous; dual-wielding vigors and weapons in the right combination makes you feel awesomely powerful, but there are enough brutally tough enemies to push you to your limits and beyond - i.e. the Firemen, the Handymen, Vox Populi armed with Hail Fire weapons and Lady Comstock. Movement around the large open environments on skylines is fast and fluid. For the toughest and most enjoyable experience the game should be played in its most difficult 1999 mode setting, which often drives you to desperation and back again but provides a whole lot of satisfaction when completing tough battles - especially the final encounter. To be successful you have to get creative and experiment with different combinations of vigors, weapons and gear. This is a game that forces you to change things up - it is not possible to stick with the same weapons and abilities all the way through. You can't rest comfortably on your laurels at any point in this game.
Art Design
This is a beautiful game. It is not photo-realistic but creates its own believable bold and bright world. Some players criticize the lack of shadows or the fact that you can't see your own feet, but those are minor considerations when there is so much to marvel at in this stunning world. It is immersive and very diverse in its locales. I did encounter some frame-rate issues in my first play-through that were solved by making some tweaks in the config files (which are easy to find online) - after that it played flawlessly.
Mood/Story
I don't think there is another game that is driven by its story to the extent that this game hangs so totally on its narrative. It is more than a game. It's more like a playable film. It actually demands more than one play-through in order to investigate what actually happens (happened/will happen...). It is a twisted tale of rebirth, redemption, nationalism, racism, oppression, revolution, murder, freewill, fate, and how physics intervenes in the relationship between a man and his daughter.
The game becomes more convoluted and affecting in its final third. The section where you have to evade the Warden of Comstock House (from whose gaze no sin escapes...) is very disturbing indeed as you nervously flit between cover surrounded by twitching, masked inter-dimensional lunatics (?!). In what other game would you be flinching at the vicious attack of a foe like the Handyman, only then to feel some kind of comical sympathy for him as he cries "I miss my own body!".
By the end of my second play-through I think (!) I have a handle on the story, and I think if Ken Levine were a film-maker, he'd be much in the mold of Scorsese or Terry Gilliam - his dystopian worlds and broken characters remind me much of The Fisher King or Brazil and his twisted stories compare with such movies as Angel Heart or Shutter Island. By the end of the game, if you really understand the story it becomes impossible to like Booker DeWitt, but you are sure glad that you followed him through this tale.
Congratulations to Irrational games on delivering a fantastic achievement. They have told an engaging, troubling and vexing grown-up story through the medium of enjoyable, strategically challenging and varied game-play. Well done.