Absolutely gorgeous to look at, and detailed up the wazoo.
The companion AI is pretty awesome. Sure it's not hard to like a gal who tosses you money and ammo (and can revive you after you've died). But I'm most impressed with the occasions where after picking through an area looking for clu... oh, who am I kidding? looking for treasure, you finally decide, okay let's go somewhere else, and rather than tagging along behind you, Elizabeth will go flying off running in front of you, usually picking the right way to go. And it's always neat to see her doing something other than standing around like a moron when you turn around and happen to look at her: she's peering here and there, or sitting bored on a bench, or possibly hyperventilating at the threat of danger.
Yes, the plot twist is pretty sweet.
Stuff blows up real good.
In Bioshock, the variety of enemies is a bit greater (or at least seems so). Sure, they're all insane drug-fiends, but the different types have different voice stylings and 'personalities' in addition to using different weapons. In Infinite, they're pretty much cops and anarchists, and there's not as much variety (and no, adding a few minibosses doesn't help).
Related to this, while fending off crazies underwater does give you the feel of 'survival horror', mowing down cops trying to apprehend you (well, okay, kill you) just doesn't feel the same. It's not scary, it's just depressing.
Perhaps as a third entry in the series, we should be jaded about guns and plasmids/vigors, but it felt to me like the game was jaded about its own mechanics. They aren't introduced to the player with the same excitement.
Some pretty big themes about race and religion are tossed out at you right at the beginning. But they don't really mean anything. The game goes out of its way to rub your face in some turn-of-the-century racism, and then... doesn't do anything with it. Alluding to powerful themes is not the same as dealing with them; nor is it 'deep'.
The antagonist is a crazy religious figure, but he has very little real screen time or voice time. He's just a bugaboo with no particular plan other than to be an antagonist. It just doesn't hold a candle to Andrew Ryan's all-too believable Randroid megalomania in the first two games. You come to know Ryan, and love the mad bastard just a little. Cutscenes may not be your thing, but it's hard to imagine something more awesome and jaw-dropping than your interview with Ryan in Bioshock. Oh, I guess Infinite has cutscenes that are eye-popping, but they don't engage the emotions enough to persuade the jaw to drop.
Slight spoiler ahead
Speaking of cutscenes -- or the equivalent -- after the interminable climactic firefight (at which I failed rather a lot, adding to my irksomeness) there is a long sequence that is not exactly a cutscene, but you are really stuck on the rails. You have no choice. Walk down there. Open that door. Press that button for the story to continue. During this, some more of the plot is revealed in dialogue and visuals, and there are a couple good tugs at the emotions here [Oh, and perhaps my favorite funny line -- you get a brief glimpse of Rapture, and Dewitt says something like "An underwater city? That's ridiculous!"] However, the lack of any choice for a pretty long sequence made it pretty annoying; it ceased to be a game way back at the end of the firefight.
Anyway, sure it didn't suck, but I think it doesn't hold a candle to the original Bioshock. The silver lining? Bioshock Infinite comes with a free copy of Bioshock. I'll probably play it again and see if my memory is wrong about how magnificent Bioshock is.