I suppose the best way to open this little review would be to admit that I found the game to be rather boring during its opening act. The campaign took me several weeks to finish simply because I initially lacked the drive to continue forward -- there was no momentum generated from narrative curiosities or profound enjoyment of the underlying mechanics, just a faint desire to continue for the sake of finishing what I'd started. Of course, this eventually changed dramatically -- for the better, I mean.
While BioInf does get credit for having the best combat in a BioShock game thus far, that's not exactly a high bar. I was initially happy with it as unarmoured enemies went down in a few shots and heavier types naturally took a bit more of a beating, however the combat quickly falls into the same trap as it does in so many games: enemies are made more powerful and more difficult to kill for seemingly no contextualised reason. They're simply harder for the sake of being harder. Consequently, the "battle arenas" that punctuate the campaign become less of something to look forward to and more of a chore (especially in later moments of the game), thanks to your shield -- which is nigh on useless even when fully upgraded -- being depleted in as little as one shot and enemies shrugging off a hail of gunfire before firing a rocket at your face. It's simply not fun. Similarly, the game's vigor system feels uninspired as most of them are little more than rebrands of their predecessor's equivalents, and the only interesting enemy type -- the Handy Man (sadly lacking the moustache that made him so distinguished in earlier footage) not being far removed from the Big Daddy. The combat in the game may be fine-tuned, but there's no escaping the feeling of "been there, done that."
Similar disappointment was found in Elizabeth -- not as a character, but as an AI companion. Throughout the game there's no shaking the feeling that she's less an assistant and more a vehicle for narrative exposition; her world interaction is limited to a few scripted moments and usefulness to the player confined to tossing you the occasional item while in combat or finding invisible coins during the quieter moments. You'd think that a young woman who'd spent almost her entire life locked away in a tower would be more interested in the big wide world. Really, for all of Irrational's talk, Elizabeth is little more than slightly repurposed Alyx.
Where the game does shine, however, is in its visual splendour*. The world of Columbia is, for the most part, meticulously crafted -- not a chapter goes by where you don't stop for a moment just to bask in the surrounding scenery. It's true that reaching Columbia lacks the sense of awe and wonder that diving down to Rapture did all those years ago, however there's no denying the city is infinitely more interesting from an aesthetic perspective. Sadly, where the world design does falter is in its lack of meaningful interactivity and decidedly dull NPCs. There are elements of interactivity peppered throughout your travels, of course, but outside of scripted moments they're limited to looting, sight-seeing and film-watching; this, coupled with the almost wax museumesque nature of the NPCs (they've no existence outside of a limited routine, if one at all) contrasting with the psychotic enemies brings to mind the artifice of it all and is consistently if only lightly distracting as a result. Much was made of Columbia being a living, breathing place, designed to be in stark contrast to the dilapidated Rapture, and while this is true to some extent, it's a shame that such little effort was put into making the world feel more alive than dead.
(*There's also, of course, the narrative, but in the interest of this being spoiler-free, I'll leave it alone.)
Overall, the fundamental problem with BioInf is that while it's a great experience, the mechanics it employs to fuel its gameplay aren't. I give it 3/4 Saoirse Ronan gifs.
Edit:
Here's my BioInf screenshot gallery. Major spoilers, obviously.